WO2025213046A1

WO2025213046A1 - Compositions and methods related to copper nanoparticles

Info

Publication number: WO2025213046A1
Application number: PCT/US2025/023193
Authority: WO
Inventors: Ariel FURST; Thomas Gill; Maggie LIU; Yan Zheng; Chao-Chi Kuo
Original assignee: Massachusetts Institute of Technology
Current assignee: Massachusetts Institute of Technology
Priority date: 2024-04-05
Filing date: 2025-04-04
Publication date: 2025-10-09
Anticipated expiration: 2026-10-05
Also published as: WO2025213023A1

Abstract

Some aspects are generally related to electrocatalysts, for example, for use during electrocatalysis. In some embodiments, the electrocatalysts may be included in a system configured to perform electrocatalysis. For instance, a system may include an electrode that is associated with a first oligo- or polynucleotide and an electrocatalyst that is associated with a second oligo- or polynucleotide. According to some such embodiments, the first and second oligo- or polynucleotides may at least partially base pair and substantially tether the electrocatalyst to the electrode. In some cases, the electrocatalyst comprises nanoparticles comprising copper (Cu), which may be suitable to be configured in a system for the electrocatalytic reduction of carbon dioxide (CO2). Some aspects are related to electrocatalysts comprising copper nanoparticles having shapes and/or compositions that may desirably affect their electrocatalytic performance, for instance, the related faradaic efficiencies and/or product distributions obtained during electrocatalysis using the nanoparticles. Still other aspects are generally directed to related methods of making and/or using the electrocatalysts and/or systems.

Description

COMPOSITIONS AND METHODS RELATED TO COPPER NANOPARTICLES

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63/575,554, filed April 5, 2024, and entitled “COMPOSITIONS AND METHODS RELATED TO COPPER NANOPARTICLES,” and to U.S. Provisional Patent Application No. 63/575,571, filed April 5, 2024, and entitled “COMPOSITIONS AND METHODS RELATED TO SURFACE-TETHERED SPECIES INCLUDING ELECTROCATALYSTS,” both of which are incorporated herein by reference in their entirety for all purposes.

TECHNICAL FIELD

Articles, systems, compositions and related methods generally related to copper nanoparticles, e.g., for electrocatalysis such as CO2 reduction, are generally described.

BACKGROUND

Catalytic conversion of chemicals is often desirable for decreasing a concentration of a reactant chemical and/or obtaining a reaction product. For example, carbon dioxide (CO2) is a byproduct of various industrial processes, and the increasing atmospheric concentration of CO2 is generally undesirable. Accordingly, electrocatalytic conversion of CO2 to various reaction products may desirably decrease an amount of atmospheric CO2 while producing valuable reaction products such as carbon monoxide, formic acid, methanol, methane, and ethylene, some of which may be used as materials in other chemical processes. However, CO2 is generally chemically inert and thus electrocatalytic conversion of CO2 using conventional systems and methods has often been inefficient. Similarly, the efficiency of other catalytic reactions may be limited by the conventionally used systems and methods. Accordingly, improved systems and methods are needed.

SUMMARY

Articles, systems, and related methods for electrocatalysis, for example, CO2 reduction, are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of one or more systems and/or articles.

Some aspects are related to compositions. In some embodiments, a composition comprises a copper nanoparticle, wherein a surface of the copper nanoparticle is essentially free of copper oxide. In some embodiments, a composition comprises a copper nanoparticle, wherein a shape of the copper nanoparticle comprises a triangular sheet and/or a jack. In some embodiments, a composition comprises a collection of copper nanoparticles, wherein at least 20% of the collection of nanoparticles define a set of nanoparticles having exposed surfaces comprising exposed lattice planes where at least 25% of the exposed lattice planes of the set are the same crystallographic lattice plane, and wherein the set of nanoparticles is not made via etching. In some embodiments, at least 50% of the nanoparticles have a triangular sheet and/or a jack shape. In some embodiments, the set of nanoparticles have a triangular sheet and/or a jack shape. In some embodiments, the copper nanoparticle has less than or equal to 6 facets. In some embodiments, an average maximum dimension of the copper nanoparticle is greater than or equal to 1 nm and less than or equal to 1000 microns. In some embodiments, the copper nanoparticles, when configured in an electrochemical cell for carbon dioxide reduction, produce a product distribution of methane to ethanol of greater than or equal to 1 to 1 and less than or equal to 1,000 to 1. In some embodiments, the copper nanoparticle is proximate a surface of an electrode. In some embodiments, the electrode comprises carbon. In some embodiments, the composition is configured for performing catalysis. In some embodiments, the composition may be used in a method, the method comprises electrocatalytically reducing CO2 using the composition. In some embodiments, the composition is configured to perform electrocatalytic CO2 reduction. In some embodiments, the turnover frequency of CO2 consumption by the copper nanoparticle is greater than or equal to 10 s’¹. In some embodiments, the turnover frequency of CO2 consumption by the copper nanoparticle is less than or equal to 10⁶ s’¹. In some embodiments, the composition is configured to produce a major product comprising ethylene during electrocatalytic CO2 reduction. In some embodiments, a shape of the copper nanoparticle comprises a triangular sheet and/or a jack. In some embodiments, a surface of the copper nanoparticle is essentially free of copper oxide. Some aspects are related to methods. In some embodiments, a method is a method for making copper nanoparticles comprising mixing a solution comprising: a monosaccharide or a disaccharide; a capping ligand; and a copper halide. In some embodiments, the monosaccharide or disaccharide comprises or is glucose, sucrose, fructose, ribose, lactose, and/or galactose. In some embodiments, the capping ligand comprises or is an amine. In some embodiments, the capping ligand comprises or is an octylamine, oleyl amine, and/or hexadecyl amine. In some embodiments, the copper halide comprises or is copper(II) chloride and/or copper(II) bromide. In some embodiments, the method further comprises heating the solution. In some embodiments, the method further comprises washing the nanoparticles. In some embodiments, the method further comprises disposing the copper nanoparticles proximate an electrode.

Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and/or inconsistent disclosure, the present specification shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

FIGS. 1A-1C are schematic diagrams of articles, systems, and methods, according to some embodiments;

FIGS. 2A-2F show characterization of copper nanoparticles, according to some embodiments;

FIGS. 3A-8 show schematic diagrams and characterization of articles and systems including molecular catalysts, according to some embodiments; FIG. 9A shows reaction conditions under which copper nanoparticles were synthesized, according to some embodiments;

FIG. 9B is an image copper nanoparticles having a shape comprising a jack, according to some embodiments;

FIGS. 9C and 9D show characterization of copper nanoparticles, according to some embodiments;

Fig. 10A shows images of copper nanoparticles, according to some embodiments; and

FIGS. 10B-10D show data associated with using the copper nanoparticles in FIG. 10A as electrocatalysts for CO2 reduction, according to some embodiments.

DETAILED DESCRIPTION

This disclosure relates to particles and other articles/compositions, linking particles and other species to surfaces such as electrodes, electrocatalysts (which can be particles) and methods of making and using these. In one set of embodiments that can apply to any of the above aspects, the disclosure provides electrocatalysts, for example, for use during electrocatalysis in systems arranged for this purpose. In some embodiments, articles, including electrocatalysts in some cases, are linked to a surface where the surface is associated with a first oligo- or polynucleotide, and the article (e.g., an electrocatalyst) is associated with a second oligo- or polynucleotide. The first and second oligo- or polynucleotides can at least partially base pair and substantially tether the article to the surface. In some cases, the article can be one or more nanoparticles, including electrocatalytic nanoparticles, comprising copper (Cu), which may be suitable to be configured in a system for the electrocatalytic reduction of carbon dioxide (CO2).

Some aspects of the disclosure are related to particles having specific new shapes, and particles (of these shapes and other shapes) that are made up, partially or fully, by a metal or combination of metals as described more fully below, for example copper nanoparticle electrocatalysts having shapes and/or compositions that desirably affect their electrocatalytic performance, for instance, the related faradaic efficiencies and/or product distributions obtained during electrocatalysis using the particles. Still other aspects are generally directed to related methods of making and/or using all of the above, including electrocatalysts and/or systems. Copper nanoparticles are described in connection with many examples and illustrations in this document, yet it is to be understood that wherever copper particles (e.g., nanoparticles) are described, embodiments may make use of other particles as described generally herein. And wherever nanoparticles are described, it is to be understood that larger particles (e.g., of metals such as copper) can be used where those embodiments are functional.

The base pairing nature of complementary oligo- and/or polynucleotides is a known and useful tool for attaching entities to surfaces. For example, oligo- and/or polynucleotides have been used to tether certain sensing entities to surfaces, where the sensing entities may be useful for sensing purposes. These sensing entities purportedly conduct small amounts of charge to facilitate sensing at the surface. However, the ability and/or efficacy of electronic conductance via base paired oligo- and/or polynucleotides between a surface to an entity attached thereto is contentious, for example, whether the conductivity is real and/or sufficient to support electrocatalysis at the entity.

In the context of the present disclosure, advantageously, it is shown that oligo- and/or polynucleotides may function as a tether between an electrocatalyst comprising a copper nanoparticle and an electrode to pass large quantities of charge sufficient for electrocatalysis. In view of this, the inventors have recognized the benefits associated with using oligo- and/or polynucleotides to tether electrocatalytic copper nanoparticles to an electrode. In some embodiments, while the electrocatalytic copper nanoparticles remain tethered to the electrode, the distance from the electrode surface introduced by the oligo- and/or polynucleotides allow the electrocatalytic copper nanoparticles to function similarly to homogeneous catalysts free in solution, e.g., having the ability to move in solution and/or have enhanced mass transport of reactants in solution to the electrocatalyst. Such homogeneous behavior of the electrocatalytic copper nanoparticles in this system is advantageously coupled to the benefits of a heterogeneous catalyst, facilitated by the oligo- and/or polynucleotide tether, such as the ability to introduce and/or alter a driving force to facilitate an electrocatalytic reaction at the nanoparticles.

Accordingly, the inventors have recognized that the systems, articles, and compositions described herein that include oligo- and/or polynucleotides as a tether between electrocatalysts and an electrode, where the electrocatalyst is a copper nanoparticle, may desirably improve electrocatalysis. For instance, in some such embodiments, copper nanoparticle electrocatalysts tethered to an electrode surface by oligo- and/or polynucleotides may efficiently reduce CO2 and advantageously produce a desired product distribution having a high amount of ethylene or other valuable products.

Some aspects are generally related systems, articles, or compositions including electrocatalysts comprising copper nanoparticles. In some embodiments, the copper nanoparticles disclosed herein have a shape that is useful for electrocatalysis, for example, due to the shape facilitating a desirable product distribution when using the copper nanoparticles for electrocatalysis. For instance, in some embodiments, the copper nanoparticles may have a shape comprising a triangular sheet, which may desirably have a product distribution during electrocatalytic CO2 reduction including a large proportion of ethylene, as described in more detail elsewhere herein. Additionally, or alternatively, according to some embodiments, the copper nanoparticles may contain a low amount of copper oxide (CuO) and/or may be substantially free of CuO, according to some embodiments. Low amounts of CuO may advantageously improve catalytic performance of the copper nanoparticles, for instance, relative to conventional Cu particles comprising more CuO. Generally, it is recognized that, in some embodiments, the copper nanoparticles comprising a triangular sheet shape and/or a low amount and/or are substantially free of CuO may advantageously improve electrocatalysis, e.g., the electrocatalytic reduction of CO2 using the copper nanoparticles. Still, some aspects of the present disclosure are generally directed to methods of making the copper nanoparticles having such a desirable shape and/or composition.

FIG. 1A shows a non-limiting example of an article 100 described herein. The article 100 includes an electrode 110, to which a first oligonucleotide 120 is chemically bound via an aniline motif. The first oligonucleotide 120 base pairs with a second oligonucleotide 122 that is chemically bound to an electrocatalyst 130, thereby connecting the electrocatalyst 130 to the electrode 110 by a double stranded oligonucleotide 124. As shown in FIG. IB, the article 100 may be incorporated into a system 150. In the embodiment shown in FIG. IB, the system 150 is an electrolyzer including a counter electrode 140, a power source 142, a membrane 144 separating the anodic and cathodic compartments of the electrolyzer and an inlet 146 and outlet 148 for solution flow, the system configured to perform electrocatalytic reduction of CO2 at the article 100. It should be understood that the foregoing example is non-limiting and that various other embodiments are also possible. Additionally, while the foregoing example and the description describes various embodiments in the context of articles comprising copper nanoparticles for the sake of simplicity, it should be understood that related compositions, systems, and methods are also possible, as this disclosure is not so limited.

The articles, systems, compositions, or methods described herein, in some embodiments, may comprise any of a variety of catalysts suitable for performing catalysis. In some embodiments, the catalyst is an electrocatalyst. The articles, systems, compositions, or methods described herein, in some embodiments, may comprise any of a variety of electrocatalysts suitable for performing electrocatalysis. In some embodiments, the electrocatalyst may be a molecular catalyst, for example, a porphyrin catalyst. In some embodiments, the electrocatalyst may be a nanoparticle. As noted above, in some embodiments, the nanoparticle comprises a metal. Various particles and nanoparticles are possible, for example, nanoparticles comprising Cu, Pt, Au, Ag, Rh, alloys thereof, and/or other suitable compositions for performing electrocatalysis. In some embodiments, the nanoparticle is a metal nanoparticle. In some embodiments, the electrocatalyst is a copper nanoparticle, which is described elsewhere herein in more detail. The particle or nanoparticle can be partially or essentially fully made of one or more metals which, when implemented in accordance with the teachings of this document, are productive. For example, particles can include one or more of silver, rhodium, gold, copper, etc., or any combination of any of these. Selection of the particle or nanoparticles for the articles described herein may be dependent based on an application of the article, for instance, a desired type of electrocatalysis, according to some embodiments. Examples of different electrocatalytic reactions for which the electrocatalysts may be used are described elsewhere herein in more detail. In some embodiments, In one specific embodiment, the nanoparticle comprises Rh. In some embodiments, the nanoparticle comprises Ag. In some embodiments, the nanoparticle comprises Cu. In some embodiments, the nanoparticle comprises Rh. According to some embodiments, the electrocatalyst may be an enzyme and/or bio-inspired molecule. Any of the foregoing catalysts may be positioned proximate an electrode surface for electrocatalysis, in accordance with some embodiments. In some such embodiments, the catalyst may be linked to the electrode via a linkage, for instance, at least partial complementary oligonucleotides as described elsewhere herein in more detail.

The article, in some embodiments, may be configured to perform any of a variety of electrocatalytic reactions. According to some embodiments, the selection of an electrocatalyst of the article may impact the efficiency of the article for performing certain electrocatalytic reactions. In some embodiments, the article may be configured to perform electrocatalytic CO2 reduction, O2 reduction, N2 reduction, O2 evolution, H2 evolution, formic acid oxidation, ethanol oxidation, and/or CO oxidation. In some embodiments, the article may be configured to perform electrocatalytic CO2 reduction. Other types of electrocatalysis are also possible using the articles described herein, as this disclosure is not so limited.

In some embodiments, the potential at which the electrocatalysis occurs depends on a variety of factors including the catalyst, electrode material, experimental setup, and electrocatalytic reaction. In some embodiments, the electrocatalysis occurs at a cathodic or anodic potential (vs RHE) of greater than or equal to -1.3 V, greater than or equal to - 1.2 V, greater than or equal to -1.1 V, greater than or equal to -1 V, greater than or equal to -0.9 V, greater than or equal to -0.8 V, greater than or equal to -0.7 V, greater than or equal to -0.6 V, greater than or equal to -0.5 V, greater than or equal to -0.4 V, greater than or equal to -0.3 V, greater than or equal to -0.2 V, greater than or equal to -0.1 V, greater than or equal to 0 V, greater than or equal to 0.1 V, greater than or equal to 0.2 V, greater than or equal to 0.3 V, greater than or equal to 0.4 V, greater than or equal to 0.5 V, greater than or equal to 0.6 V, greater than or equal to 0.7 V, greater than or equal to 0.8 V, greater than or equal to 0.9 V, greater than or equal to 1 V, greater than or equal to 1.1 V, greater than or equal to 1.2 V, greater than or equal to 1.3 V, greater than or equal to 1.4 V, greater than or equal to 1.5 V, or greater than or equal to 1.6 V. In some embodiments, the electrocatalysis occurs at a cathodic or anodic potential (vs RHE) of less than or equal to 1.7 V, less than or equal to 1.6 V, less than or equal to 1.5 V, less than or equal to 1.4 V, less than or equal to 1.3 V, less than or equal to 1.2 V, less than or equal to 1.1 V, less than or equal to 1 V, less than or equal to 0.9 V, less than or equal to 0.8 V, less than or equal to 0.7 V, less than or equal to 0.6 V, less than or equal to 0.5 V, less than or equal to 0.4 V, less than or equal to 0.3 V, less than or equal to 0.2 V, less than or equal to 0.1 V, less than or equal to 0 V, less than or equal to -0.1 V, less than or equal to -0.2 V, less than or equal to -0.3 V, less than or equal to -0.4 V, less than or equal to -0.5 V, less than or equal to -0.6 V, less than or equal to -0.7 V, less than or equal to -0.8 V, less than or equal to -0.9 V, less than or equal to -1 V, less than or equal to -1.1 V, or less than or equal to -1.2 V. Combinations of the foregoing ranges are possible. Other ranges are also possible.

In some embodiments, using the electrocatalyst in the systems described herein for electrocatalysis may result in a faradaic efficiency for the major reaction product of the electrocatalytic reaction of greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, or greater than or equal to 90%. In some embodiments, the faradaic efficiency for the major reaction product of the electrocatalytic reaction is less than or equal to 100%, less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 50% and less than or equal to 100%, greater than or equal to 70% and less than or equal to 80%). Other ranges are also possible.

Some aspects of the present disclosure are generally related copper nanoparticles, e.g., within compositions, articles, systems, and/or methods. In some such embodiments, the copper nanoparticles may be electrocatalysts. It should be understood that when described herein, a “nanoparticle” may refer to the generally meaning understood to those of ordinary skill in the art and/or may refer to a microparticle. Nanoparticles are generally understood to be particles of a material having a diameter (e.g., an average maximum dimension) of greater than or equal to 1 nm and less than or equal to 100 nm. In the context of this disclosure, nanoparticle may also refer to particles having a diameter (e.g., an average maximum dimension) of up to 1000 microns. In some embodiments, an average maximum dimension of a nanoparticle is greater than or equal to 1 nm, greater than or equal to 3 nm, greater than or equal to 5 nm, greater than or equal to 10 nm, greater than or equal to 20 nm, greater than or equal to 30 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 150 nm, greater than or equal to 200 nm, greater than or equal to 250 nm, greater than or equal to 300 nm, greater than or equal to 350 nm, greater than or equal to 400 nm, greater than or equal to 500 nm, greater than or equal to 600 nm, greater than or equal to 700 nm, greater than or equal to 800 nm, greater than or equal to 900 nm, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 50 microns, greater than or equal to 100 microns, greater than or equal to 200 microns, greater than or equal to 300 microns, greater than or equal to 500 microns, or greater than or equal to 800 microns. According to some embodiments, an average maximum dimension of a copper nanoparticle is less than or equal to 1000 microns, less than or equal to 800 microns, less than or equal to 500 microns, less than or equal to 300 microns, less than or equal to 200 microns, less than or equal to 100 microns, less than or equal to 50 microns, less than or equal to 10 microns, less than or equal to 8 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 900 nm, less than or equal to 800 nm, less than or equal to 700 nm, less than or equal to 600 nm, less than or equal to 500 nm, less than or equal to 400 nm, less than or equal to 350 nm, less than or equal to 300 nm, less than or equal to 250 nm, less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, less than or equal to 50 nm, less than or equal to 30 nm, less than or equal to 20 nm, less than or equal to 10 nm, less than or equal to 5 nm, or less than or equal to 3 nm. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 1 nm and less than or equal to 1000 microns, greater than or equal to 1 nm and less than or equal to 100 nm, greater than or equal to 1 nm and less than or equal to 10 microns, greater than or equal to 100 nm and less than or equal to 1000 microns, greater than or equal to 100 nm and less than or equal to 1 micron). Other ranges are also possible.

A nanoparticle may have any of a variety of suitable shapes, in accordance with some embodiments. According to some embodiments, the nanoparticle may be substantially a sphere, cube, tetrahedron, octahedron, cuboctahedron, a corner-truncated octahedron, truncated octahedron, edge-truncated rhombic dodecahedron, rhombi- truncated cube, edge-truncated cube, or any of a variety of other regular or irregular shapes.

The copper nanoparticles may have any of variety of suitable shapes, according to some embodiments. Non-limiting shapes of the copper nanoparticle include a sphere, a triangular sheet, a jack, a tapered triangle, a wire, a cube, a rod, a triangular prism, a truncated octahedron, a sphere, and/or a pointy leaf, in accordance with some embodiments. Other shapes are also possible. In some embodiments, the shape of the copper nanoparticle comprises or may be a triangular sheet and/or a jack. In some embodiments, the shape of the copper nanoparticle may be a triangular sheet. In some embodiments, the shape of the copper nanoparticle may be a jack. Other shapes are also possible, as this disclosure is not so limited. Some aspects of the present application are related to nanoparticles having certain shapes that may advantageously provide improved performance, for example, during electrocatalysis.

In some embodiments, a nanoparticle shaped as a triangular sheet may have a two- dimensional (2D) projection in at least one direction that is triangular, wherein a thickness of the nanoparticle in a direction perpendicular to the plane of the projection is smaller than a maximum dimension of the projection. For instance, in some embodiments, a maximum dimension of the 2D projection in a first direction of the plane and in a second direction of the plane may independently be any of the foregoing dimensions (e.g., at least 1 nm and less than 1000 microns), and a thickness of the nanoparticle in a dimension perpendicular to the plane is less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 20%, less than or equal to 10%, less than or equal to 5%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.5%, or less than or equal to 0.1% of the maximum dimension in the first direction of the plane and/or in the second direction of the plane. As a nonlimiting example, a nanoparticle having a triangular sheet shape may have a 2D projection that is triangular, where a maximum dimension in a first direction of the plane of the projection is greater than 1 micron and a maximum dimension in a second of the plane of the projection is greater than 1 micron, and a thickness of the nanoparticle perpendicular to the first and second directions is less than or equal to 100 nm, less than or equal to 50 nm, less than or equal to 20 nm, or less. A non-limiting example of a copper nanoparticle having a triangular sheet shape is shown in FIG. 9C.

According to some embodiments, copper nanoparticles having certain shapes may advantageously produce different product distributions during electrocatalysis, relative to typically shaped nanoparticles (e.g., spherical). Without wishing to be bound by any particular theory, the shape of the copper nanoparticle is related to the types of surface and edge sites exposed to reactants, which is believed to influence the reaction pathway during electrocatalysis and thus the reaction product distribution. In some embodiments, when the copper nanoparticle is shaped like a triangular sheet, the copper nanoparticle may desirably produce a high proportion of ethylene during CO2 reduction. In some embodiments, when the copper nanoparticle is shaped like a triangular sheet, the copper nanoparticle may desirably produce a high proportion of CO during CO2 reduction. Certain CO2 reaction products, such as ethylene, CO, alcohols, and/or hydrocarbons may be desirable as useful starter chemical for certain chemical processes. Thus, in some embodiments, the various product distributions obtained from electrocatalytic CO2 reduction using the copper nanoparticles described herein may be desirable.

In some embodiments, it may be desirable to use copper nanoparticles having a shape comprising a triangular sheet. In some such embodiments, the copper nanoparticles may have an improved electrocatalytic performance, for example, towards the electrocatalytic reduction of the CO2. In some embodiments, the product distribution produced during the electrocatalytic reduction of the CO2 using the copper nanoparticles comprising a triangular sheet shape may have a desirable major product faradaic efficiency.

It should be understood that any composition, article, system, or method described herein comprising a nanoparticle may comprise a plurality of nanoparticles. In some embodiments, the plurality of nanoparticles may be referred to as a collection of nanoparticles. As a non-limiting example, the plurality of nanoparticles, according to some embodiments, may be present on and/or proximate a surface of an electrode. In some embodiments, the plurality of nanoparticles may be linked to an electrode via a linker, such as one or more oligo and/or polynucleotides, as described in more detail elsewhere herein.

The plurality of nanoparticles may be present in any of a variety of suitable amounts, in accordance with some embodiments. In some embodiments, the plurality of nanoparticles may be present proximate to and/or on a surface (e.g., a non-smooth surface of an electrode). In some embodiments, the plurality of nanoparticles may be present in a solution.

Where particles such as nanoparticles (or any other entity) are positioned proximate a surface, it can be positioned in contact with the surface or at a position relative to the surface (at a selected distance or within a range of distances from the surface) selected to provide a desired effect. Where the entity is positioned relative to the surface can be selected by those of ordinary skill in the art, with the benefit of this disclosure, without undue experimentation. How such an entity is positioned relative to the surface is also routine for those of ordinary skill in the art based upon this disclosure. For example, an entity can be suspended in a fluid close to or in contact with the surface such that some or all of the entity or entities are positioned proximate the surface regardless of whether it or they are in contact with the surface. In such a case, some entities may contact the surface, some entities may be close to the surface, and some entities may be distant enough from the surface that they are not affected appreciably by the surface and in many cases that is acceptable. In other cases, entities are positioned at a surface or close enough to the surface that essentially all of them, or a significant portion of them, e.g. at least 30%, 50%, 70%, or 90% or more are affected by the entity/surface relationship.

Entities can be positioned proximate a surface via an intervening material such as a layer or set of layers that can hold the entity proximate the surface. For example, a layer that adheres to a surface and also adheres to the entities and does not interfere appreciably with or perhaps even enhances interaction between the entity and the surface can be selected. Entities can be held proximate a surface by electrostatic interaction via applied charge to the surface and or entity, induced (rather than applied) charge difference, ionic interactions, covalent interactions, weak forces such as hydrogen bonding and/or Van der Walls interactions, etc. In one set of embodiments, entities are positioned proximate a surface via tethering involving a molecular linker or linkers. A molecular linker(s) can be an oligonucleotide or polynucleotides, such as are described herein.

In some embodiments, the catalyst (e.g., nanoparticle, copper nanoparticles) may be proximate a surface of an electrode in any suitable amount. For instance, in some embodiments, the catalyst may be present on a surface in a density of greater than or equal to 3 pmol/cm², greater than or equal to 4 pmol/cm², greater than or equal to 5 pmol/cm², greater than or equal to 6 pmol/cm², greater than or equal to 7 pmol/cm², greater than or equal to 8 pmol/cm², greater than or equal to 9 pmol/cm². In some embodiments, the catalyst may be present on the surface in a density of less than or equal to 10 pmol/cm², less than or equal to 9 pmol/cm², less than or equal to 8 pmol/cm², less than or equal to 7 pmol/cm², less than or equal to 6 pmol/cm², less than or equal to 5 pmol/cm², less than or equal to 4 pmol/cm². Combinations of the foregoing ranges are possible (e.g., greater than or equal to 3 pmol/cm² and less than or equal to 10 pmol/cm²). Other ranges are also possible.

According to some embodiments, the plurality of nanoparticles (e.g., a collection of nanoparticles or a collection of copper nanoparticles) may be made by any of a variety of suitable methods, as described elsewhere herein. In some embodiments, methods may include seed-mediated growth, electrodeposition, sol-gel deposition, emulsion-based methods, lithography, vapor deposition (e.g., chemical vapor deposition), and/or precipitation methods. Other methods are also possible. In some embodiments, nanoparticles may be acquired, e.g., from a commercial source. In some embodiments, the plurality of nanoparticles is not made by etching.

According to some embodiments, the nanoparticles of the plurality of nanoparticles have a desirable crystallography plane or lattice plane. Those of ordinary skill in the art will understand that the lattice planes defined by each of the nanoparticles may be determined by the miller indices of the nanoparticles, e.g., via x-ray diffraction. According to some embodiments, at least 20%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the nanoparticles of the plurality of nanoparticles may define a set of exposed surfaces comprises exposed lattice planes. According to some embodiments, no more than 100%, no more than 90%, no more than 80%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, or no more than 30% of the nanoparticles of the plurality of nanoparticles may define a set of exposed surfaces comprises exposed lattice planes. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 20% and no more than 100%). Other ranges are possible.

In some embodiments, a portion of the set of exposed lattice planes of the set are the same crystallographic lattice plane (e.g., the same type of lattice plane). The exposed lattice planes may be determined, in some embodiments, using X-ray diffraction spectroscopy (XRD). According to some embodiments, this may advantageously allow the nanoparticles to efficiently catalyze a reaction at the set of exposed lattice planes (e.g., leading to improved catalysis when using the plurality of nanoparticles, as described elsewhere herein). In some embodiments, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the set of exposed lattice planes are the same lattice plane (e.g., the same type of lattice plane). According to some embodiments, no more than 100%, no more than 90%, no more than 80%, no more than 70%, no more than 60%, no more than 50%, no more than 40%, or no more than 30% of the set of exposed lattice planes are the same lattice plane (e.g., the same type of lattice plane). Combinations of the foregoing ranges are possible (e.g., at least 25% and no more than 100%). Other ranges are also possible.

According to some embodiments, the nanoparticles of the plurality of nanoparticles may have any of a variety of suitable shapes, as described in more detail elsewhere herein. In some embodiments, a relatively large portion of the nanoparticles of the plurality of nanoparticles may desirably include or be certain shapes, as these shapes may improve electrocatalysis relative to electrocatalysis performed using nanoparticles having a different shape (e.g., but may comprise the same components). In some embodiments, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the nanoparticles of the plurality of nanoparticles comprise a first shape. In some embodiments, no more than 100%, no more than 90%, no more than 80%, no more than 70%, or no more than 60% of the nanoparticles of the plurality of nanoparticles comprise a first shape. Combinations of the foregoing ranges are possible (e.g., at least 50% and no more than 100%). Other ranges are also possible. For instance, in some embodiments, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the nanoparticles of the plurality of nanoparticles have a shape comprising a triangular sheet and/or a jack shape. In some embodiments, no more than 100%, no more than 90%, no more than 80%, no more than 70%, or no more than 60% of the nanoparticles of the plurality of nanoparticles have a shape comprising a triangular sheet and/or a jack shape. Combinations of the foregoing ranges are possible (e.g., at least 50% and no more than 100%). Other ranges are also possible.

In some embodiments, the copper nanoparticle consists essentially of Cu. In some embodiments, the copper nanoparticle consists of Cu. For example, in some embodiments, the copper nanoparticle has a low amount of copper oxide (CuO). In some embodiments, the copper nanoparticle is substantially free of CuO. In some embodiments, the copper nanoparticle is essentially free of CuO. In some embodiments, the presence and/or quantity of CuO on the surface of the copper nanoparticles may be determined using X-ray diffraction spectroscopy (XRD). In some embodiments, less than 50 wt%, less than 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 5 wt%, less than or equal to 3 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.5 wt%, less than or equal to 0.1 wt%, or less of the copper nanoparticle is CuO. According to some embodiments, a low amount of CuO (e.g., as in the foregoing ranges) present on the copper nanoparticle may lead to the better electrocatalytic performance of the copper nanoparticle, e.g., as compared to a copper nanoparticle including a larger amount of CuO.

The article, in some embodiments, may comprise an electrocatalyst comprising a copper nanoparticle and may be configured to perform any of a variety of electrocatalytic reactions. According to some embodiments, the selection of an electrocatalyst of the article may impact the efficiency of the article for performing certain electrocatalytic reactions. In some embodiments, the article may be configured to perform electrocatalytic CO2 reduction, O2 reduction, N2 reduction, O2 evolution, H2 evolution, formic acid oxidation, ethanol oxidation, and/or CO oxidation. In some embodiments, the article may be configured to perform electrocatalytic CO2 reduction. In some such embodiments, the article including the electrocatalyst comprises a copper nanoparticle may be configured to perform electrocatalytic CO2 reduction and may form CO, methanol, ethanol, ethylene, formate (e.g., formic acid), and/or methane. Other reaction products are also possible. Other types of electrocatalysis are also possible using the articles described herein, as this disclosure is not so limited. It will be understood that the articles described herein may further be incorporated into systems configured to perform certain electrocatalytic reactions, e.g., as those described above.

In some embodiments, the potential at which the electrocatalysis occurs depends on a variety of factors including the electrode material, experimental setup, and desired electrocatalytic reaction. In some embodiments, the electrocatalysis occurs at a cathodic potential (vs RHE) of greater than or equal to -1.3 V, greater than or equal to -1.2 V, greater than or equal to -1.1 V, greater than or equal to -1 V, greater than or equal to -0.9 V, greater than or equal to -0.8 V, greater than or equal to -0.7 V, greater than or equal to -0.6 V, greater than or equal to -0.5 V, greater than or equal to -0.4 V, greater than or equal to -0.3 V, greater than or equal to -0.2 V, greater than or equal to -0.1 V, greater than or equal to 0 V, greater than or equal to 0.1 V, greater than or equal to 0.2 V, greater than or equal to 0.3 V, greater than or equal to 0.4 V, greater than or equal to 0.5 V, greater than or equal to 0.6 V, greater than or equal to 0.7 V, greater than or equal to 0.8 V, greater than or equal to 0.9 V, greater than or equal to 1 V, greater than or equal to 1.1 V, greater than or equal to 1.2 V, greater than or equal to 1.3 V, greater than or equal to 1.4 V, greater than or equal to 1.5 V, or greater than or equal to 1.6 V. In some embodiments, the electrocatalysis occurs at a cathodic potential (vs RHE) of less than or equal to 1.7 V, less than or equal to 1.6 V, less than or equal to 1.5 V, less than or equal to 1.4 V, less than or equal to 1.3 V, less than or equal to 1.2 V, less than or equal to 1.1 V, less than or equal to 1 V, less than or equal to 0.9 V, less than or equal to 0.8 V, less than or equal to 0.7 V, less than or equal to 0.6 V, less than or equal to 0.5 V, less than or equal to 0.4 V, less than or equal to 0.3 V, less than or equal to 0.2 V, less than or equal to 0.1 V, less than or equal to 0 V, less than or equal to -0.1 V, less than or equal to -0.2 V, less than or equal to -0.3 V, less than or equal to -0.4 V, less than or equal to -0.5 V, less than or equal to -0.6 V, less than or equal to -0.7 V, less than or equal to -0.8 V, less than or equal to -0.9 V, less than or equal to -1 V, less than or equal to -1.1 V, or less than or equal to -1.2 V. Combinations of the foregoing ranges are possible. Other ranges are also possible.

In some embodiments, the current density at which the electrocatalysis occurs depends on a variety of factors including the catalyst, electrode material, experimental setup, and electrocatalytic reaction. In some embodiments, the electrocatalysis occurs at a current density of greater than or equal to 1 mA/cm², greater than or equal to 10 mA/cm², greater than or equal to 100 mA/cm², greater than or equal to 500 mA/cm², or greater than or equal to 1 A/cm². In some embodiments, the electrocatalysis occurs at a current density of less than or equal to 10 A/cm², less than or equal to 1 A/cm², less than or equal to 500 mA/cm², less than or equal to 100 mA/cm², or less than or equal to 10 mA/cm². Combinations of the foregoing ranges are possible (e.g., greater than or equal to 1 mA/cm² and less than or equal to 10 A/cm²). Other ranges are also possible. It will be appreciated that the use of oligonucleotide-tethered and/or polynucleotide tethered catalysts (e.g., electrocatalysts, nanoparticles, copper nanoparticles) on electrodes has not previously been used to pass such current densities for electrocatalysis. Similarly, it will be appreciated that the magnitude of current passed at an article or system including an electrode on which catalysts (e.g., electrocatalysts, nanoparticles, copper nanoparticles) are tethered via oligonucleotide and/or polynucleotide are higher than previous systems. For instance, in some embodiments, the article may be configured to pass greater than or equal to 1 micro A, greater than or equal to 10 micro A, greater than or equal to 100 micro A, greater than or equal to 1 mA, greater than or equal to 10 mA, greater than or equal to 100 mA, or greater than or equal to 1 A of current. In some embodiments, the article may be configured to pass less than or equal to 10 A, less than or equal to 1 A, less than or equal to 100 mA, less than or equal to 10 mA, less than or equal to 1 mA, less than or equal to 100 micro A, or less than or equal to 10 micro A of current. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 1 microA and less than or equal to 10 A of current). Other ranges are also possible.

In some embodiments, the catalyst (e.g., electrocatalyst, nanoparticle, copper nanoparticles) may have any of a variety of suitable activities when configured in the articles described herein. In some embodiments, the catalyst may have an activity of greater than or equal to 10³ A/gram of catalyst, greater than or equal to 10⁴ A/gram of catalyst, greater than or equal to 10⁵ A/gram of catalyst, greater than or equal to 10⁶ A/gram of catalyst, greater than or equal to 10⁷ A/gram of catalyst, greater than or equal to 10⁸ A/gram of catalyst, greater than or equal to 10⁹ A/gram of catalyst. In some embodiments, the catalyst may have an activity of less than or equal to 10¹⁰ A/gram of catalyst, less than or equal to 10⁹ A/gram of catalyst, less than or equal to 10⁸ A/gram of catalyst, less than or equal to 10⁷ A/gram of catalyst, less than or equal to 10⁶ A/gram of catalyst, less than or equal to 10⁵ A/gram of catalyst_i or less than or equal to 10⁴ A/gram of catalyst. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 10³ A/gram of catalyst and less than or equal to 10¹⁰ A/gram of catalyst). Other ranges are also possible.

It will be understood that, in some embodiments, the faradaic efficiency and/or the current density of electrocatalysis is affected by certain mass transport limitations. For instance, faradaic efficiency may decrease in some embodiments as a driving force increases and/or an amount of a reactant decreases. Accordingly, in some embodiments, electrocatalysis may be designed to increase mass transport to a surface of an electrode and/or catalysts (e.g., electrocatalysts, nanoparticles, or the like as described elsewhere herein) via flow-based systems, bubbling a reactant, increased convection, or the like.

In some embodiments, the electrocatalyst may have a desirable faradaic efficiency for the major reaction product of the electrocatalytic reaction. In some embodiments, the electrocatalyst comprising copper nanoparticles may have a desirable faradaic efficiency for the major reaction product of the electrocatalytic reaction. The faradaic efficiency for the major reaction product is the ratio (e.g., percentage) of the number of electrons utilized to produce the major product over the number of electrodes input into the system. The faradaic efficiency for the major product (e.g., or other products) may be calculated by measuring an amount of produced product, determining the amount of electrons utilized to produce the produced product, and then dividing this number by the amount of electrons input into the system (e.g., as determined by a current or current density during electrocatalysis). In some embodiments, the electrocatalyst may have a faradaic efficiency for the major reaction product of the electrocatalytic reaction of greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, or greater than or equal to 90%. In some embodiments, the faradaic efficiency for the major reaction product of the electrocatalytic reaction is less than or equal to 100%, less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 50% and less than or equal to 100%, greater than or equal to 70% and less than or equal to 80%). Other ranges are also possible.

In some embodiments, the electrocatalyst of the system, article, or composition is a copper nanoparticle and has a faradaic efficiency for the major product of the CO2 of greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, or greater than or equal to 90%. In some embodiments, the faradaic efficiency for the major product of the CO2 reduction is less than or equal to 100%, less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 50% and less than or equal to 100%, greater than or equal to 70% and less than or equal to 80%). Other ranges are also possible. In some embodiments, the major reaction product of CO2 reduction is ethylene. In some embodiments, the major reaction product of CO2 reduction is CO. In some embodiments, the major reaction product of CO2 reduction is ethanol. According to some embodiments, nanoparticles having certain shapes may yield desirable product distributions. Thus, in some embodiments, articles, systems, compositions, methods, or the like may be designed with certain nanoparticles having desired shapes to attain certain product distributions.

In some embodiments, a copper nanoparticle having a shape comprising a triangular sheet, when configured and used to perform electrocatalysis, may have a faradaic efficiency for the major product of CO2 reduction of greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, or greater than or equal to 90%. In some embodiments, the faradaic efficiency for the major product of CO2 reduction is less than or equal to 100%, less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 50% and less than or equal to 100%, greater than or equal to 70% and less than or equal to 80%). Other ranges are also possible. In some embodiments, the major reaction product of CO2 reduction is ethylene. In some embodiments, the major reaction product of CO2 reduction is CO. In some embodiments, the major reaction product of CO2 reduction is ethanol. According to some embodiments, the copper nanoparticle having a shape comprising a triangular sheet may have a high faradaic efficiency when producing ethylene from the electrocatalytic reduction of CO2.

In some embodiments, a copper nanoparticle may exhibit a relatively high turnover frequency during catalysis (e.g., electrocatalysis). For example, in some embodiments, the turnover frequency at the copper nanoparticle for CO2 reduction is greater than or equal to 10 s’¹, greater than or equal to 10² s’¹, greater than or equal to 10³ s’¹, greater than or equal to 10⁴ s’¹, or greater than or equal to 10⁵ s’¹. In some embodiments, the turnover frequency at the copper nanoparticle for CO2 reduction is less than or equal to 10⁶ s’¹, less than or equal to 10⁵ s’¹, less than or equal to 10⁴ s’¹, less than or equal to 10³ s’¹, or less than or equal to 10² s’¹. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 10 s’¹ and less than or equal to 10⁶ s’¹). Other ranges are also possible. In some embodiments, the nanoparticles are capped with a ligand. In some embodiments, the nanoparticles comprise Cu, and are capped with a ligand. In some embodiments, the capping ligand is an organic molecule. In some such embodiments, the organic molecule includes an amine. According to some embodiment, the capping ligand comprises or is hexadecyl amine, octadecyl amine, and/or oleyl amine. In some embodiments, the capping ligand comprises or is hexadecylamine. In some embodiments, as described elsewhere herein, the presence of a capping ligand arises due to a method of making the copper nanoparticles. In some such embodiments, the presence of the capping ligand may be desirable, e.g., for reducing the amount of CuO present on the copper nanoparticles before performing electrolysis.

In some embodiments, a system including an electrode may be described. In some embodiments, the material of the electrode may be any of a variety of materials suitable for performing electrochemistry, e.g., platinum, gold, carbon, or other appropriate materials. In some embodiments, it may be desirable to use a screen -printed electrode (e.g., comprising carbon) or carbon paper electrode, as the cost of the system may be low, for example, when compared to using other electrode materials. According to some embodiments, carbon-based electrodes may advantageously facilitate chemical bonds between the electrode and other components of the system (e.g., a first oligo- or poly nucleotide). In some embodiments, the electrode may provide electrical communication to, and thus facilitate electrocatalysis at, an electrocatalyst (e.g., a copper nanoparticle) associated with the electrode.

According to some embodiments, the electrode may have a non-smooth surface, and using such an electrode in the systems described herein may advantageously improve catalysis. For example, in some embodiments, an article may include an electrode having a non-smooth surface and a catalyst proximate the non-smooth surface, such as an electrocatalyst proximate the non-smooth surface. In some such embodiments, the electrocatalyst can be positioned proximate the non-smooth surface via linkage comprising a first linker immobilized on the surface, the first linker comprising a polynucleotide and/or an oligonucleotide; and a second linker associated with the copper nanoparticle, the second linker comprising a polynucleotide and/or an oligonucleotide, wherein at least a portion of the second linker is complementary to at least a portion of the first linker. In some such embodiments, the first and second linkers are at least partially base paired. In some embodiments, the electrode having a non-smooth surface comprises carbon. In some embodiments, the electrode having a non-smooth surface comprises a carbon cloth.

Non-smooth surfaces that can provide improved performance can be any that include irregularities or indentations such as those defined by a cloth such as a woven cloth, but the non-smooth surface need not to be a cloth. In one set of embodiments the non- smooth surface has irregularities that are of the same general dimension and spacing of those created by adjacent fibers (such as weft and weave) of a woven cloth. In other arrangements different sizes, spacings, and shapes of irregularities such as protrusions and indentations, or undulations, steps, and/or waves, are selected via simple experimentation to provide improved performance over a smooth surface. Depending upon the particular purpose, including but not limited to catalysis, electrocatalysis, or the like, different non-smooth surfaces may provide different benefits, and surfaces can be easily experimentally selected because of ordinary skill in the art based upon the teachings of this disclosure.

The electrocatalyst (e.g., a copper nanoparticle) may be associated with the electrode in any of a variety of ways. For example, in some embodiments, the electrocatalyst may be proximate a surface of the electrode. In some such embodiments, the electrocatalyst may be present within an electrically conductive ink disposed on the surface of the electrode. In some embodiments, the electrode may be linked to the electrocatalyst via one or more linkers.

An electrode may be linked to an electrocatalyst by one or more linkers, according to some embodiments, within an article, system, and/or method. In some embodiments, a system may include one or more linkers. In some embodiments, one or more linkers may comprise oligo- and/or polynucleotides (e.g., nucleic acids). In some such embodiments, the one or more oligo- and/or polynucleotides comprise nucleotides (e.g., containing nucleobases cytosines, guanines, adenines, thymines, uracils, or modified nucleobases). In some embodiments, the system may include a first oligo- and/or polynucleotide associated with the electrode and a second oligo- and/or polynucleotide associated with the electrocatalyst. In some such embodiments, the first and second oligo- and/or polynucleotides are at least partially complementary, such that they may associate with each other by at least partially base pairing together. The one or more linkers may have any of a variety of number of constituent molecules, in some embodiments. For example, in some cases, the one or more linkers may comprise oligo- or polynucleotides, with any of a variety of suitable number of constituent nucleotides. According to some embodiments, it may be desirable for a system or article including one or more oligo- or polynucleotides to comprise oligo- or polynucleotides having small numbers of nucleotides so that, when base paired with an at least partially complementary oligo- or polynucleotide, a length of the resulting paired oligo- or polynucleotides is short to facilitate electrical conduction, e.g., between an electrode and an electrocatalyst.

In some embodiments, a first or second oligo- or polynucleotides may each independent have greater than or equal to 5, greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, greater than or equal to 225, greater than or equal to 250, greater than or equal to 300, greater than or equal to 350, greater than or equal to 400, greater than or equal to 450, greater than or equal to 500, greater than or equal to 600, greater than or equal to 700, greater than or equal to 800, greater than or equal to 900 nucleotides, greater than or equal to 1000 nucleotides, or greater than or equal to 5000 nucleotides. In some embodiments, a first or second oligo- or polynucleotides may each independent have less than or equal to 10000, less than or equal to 5000, less than or equal to 1000, less than or equal to 900, less than or equal to 800, less than or equal to 700, less than or equal to 600, less than or equal to 500, less than or equal to 450, less than or equal to 400, less than or equal to 350, less than or equal to 300, less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 40, less than or equal to 30, less than or equal to 20, or less than or equal to 10 nucleotides. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 5 and less than or equal to 1000 nucleotides). Other ranges are also possible.

The nucleotides in the first or second oligo- or polynucleotide may be selected randomly or selected intentionally (e.g., the order of the sequence of cytosines, guanines, adenines, thymines, etc.), so long as the corresponding first or second oligo- or polynucleotide are at least partially complementary. The first and second oligo- or polynucleotides being at least partially complementary may facilitate, in some embodiments, base pairing therebetween such that the first and second oligo- or polynucleotides associate together. In some embodiments the first and second oligo- or polynucleotides are at least partially base paired together, e.g., within the article or system. In some embodiments the first and second oligo- or polynucleotides are completely complementary. In some such embodiments, the first and second oligo- or polynucleotides are configured to be substantially completely base paired, e.g., within the article or system. According to some embodiments, the extent of base pairing (e.g., due to complementary base pairs on the first and second oligo- or polynucleotides) may maintain a position of the first and/or second oligo- or polynucleotide, relative to the other oligo- or polynucleotide. For example, in some embodiments, the first and second oligo- or polynucleotides are configured such that greater than or equal to 3, greater than or equal to 5, greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, greater than or equal to 225, greater than or equal to 250, greater than or equal to 300, greater than or equal to 350, greater than or equal to 400, greater than or equal to 450, greater than or equal to 500, greater than or equal to 600, greater than or equal to 700, greater than or equal to 800, or greater than or equal to 900 nucleotides base pair. In some embodiments, the first and second oligo- or polynucleotides are configured such that less than or equal to 1000, less than or equal to 900, less than or equal to 800, less than or equal to 700, less than or equal to 600, less than or equal to 500, less than or equal to 450, less than or equal to 400, less than or equal to 350, less than or equal to 300, less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 40, less than or equal to 30, less than or equal to 20, less than or equal to 10 nucleotides, less than or equal to 5 nucleotides. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 3 and less than or equal to 1000 nucleotides). Other ranges are also possible. Accordingly, in some embodiments, at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70%, and/or no more than 80%, no more than 90%, up to 100% of the base pairs of the first and second oligo- or polynucleotides may be complementary.

As described above, a first oligo- or polynucleotide may be associated with an electrode, e.g., a surface of the electrode, in some embodiments. According to some embodiments, the first oligo- or polynucleotide may be chemically bound to the electrode. Any of a variety of suitable chemistries may be used to chemically bind the first oligo- or polynucleotide to the electrode, in some embodiments, which may be selected based on the identity of the electrode. For example, in some embodiments, the electrode may be a gold electrode, and thus the first oligo- or polynucleotide may be synthesized to terminate in a thiol-containing group to form a dative bond with the gold electrode. Dative bonds are also possible with electrode materials other than gold. In some embodiments, the electrode may be a carbon electrode. In some such embodiments, the carbon surface may be bound to the first oligo- or polynucleotide through biorthogonal chemistries, oxidative coupling reactions, and/or reductive coupling reactions. In some such embodiments, the first oligo- or polynucleotide may be synthesized to terminate in a group that is suitable for activating and/or bonding to the surface of the electrode. In some embodiments, the first oligo- or polynucleotide and the electrode may form a chemical bond therebetween. The material of the electrode, and thus the chemistry used to chemically bind the oligo-or polynucleotide to the electrode, may be selected based on the reaction conditions for which the electrode may be used. For example, in some embodiments, a gold electrode chemically bonded to a nucleotide (e.g., an oligo or polynucleotide) via a dative bond is unsuitable for used in CO2 reduction because the reaction conditions are too harsh to maintain the dative bond. Alternatively, a carbon-based electrode may be modified to covalently bond the to the oligo- or polynucleotide.

Similarly to a first oligo- or polynucleotide being associated with an electrode as described above, a second oligo- or polynucleotide may be associated with an electrocatalyst. According to some embodiments, the second oligo- or polynucleotide may be chemically bound to the electrocatalyst. Any of a variety of suitable chemistries may be used to chemically bind the second oligo- or polynucleotide to the electrocatalyst, in some embodiments, which may be selected based on the identity of the electrocatalyst. For example, in some embodiments, the electrocatalyst is a copper nanoparticle, where the second oligo- or polynucleotide may be bound to the copper nanoparticle by a dative bond formed with a sulfur or nitrogen containing compound. In some embodiments, the electrocatalyst may be bound to the second oligo- or polynucleotide through a chemical bond formed via an oxidative coupling reaction. In some embodiments, the second oligo- or polynucleotide may be synthesized to terminate in a suitable reactive group that is configured to be activated and/or bound to the electrocatalyst, e.g., through an oxidative coupling reaction.

According to some embodiments, because the first oligo- or polynucleotide is associated with the electrode and the second oligo- or polynucleotide associated with an electrocatalyst (e.g., a copper nanoparticle), at least partial base pairing between the first and second oligo- or polynucleotides may result in an association between the electrode and the electrocatalyst. For instance, the chemical bonding (e.g., base pairing) between the first oligo- or polynucleotide and the electrode coupled with the chemical bond between the second oligo- or polynucleotide and the electrocatalyst may maintain a proximity between the electrocatalyst and the electrode, e.g., following at least partial base pairing between the first and second oligo- or polynucleotides.

Additionally, in some embodiments, the distribution of the first oligo- or polynucleotide on the electrode may determine the spatial distribution of the electrocatalyst on the surface of the electrode (e.g., after the oligo- or polynucleotides base pair). In some such embodiments, the systems and articles described here may facilitate the loading and/or spacing of electrocatalysts on the surface of the electrode.

Associating an electrocatalyst (e.g., a copper nanoparticle) to an electrode via complementary oligo- or polynucleotides as described herein, in accordance with some embodiments, may provide a variety of benefits over conventional systems, for example, where an electrocatalyst may be present within an ink disposed on an electrode. For instance, in some embodiments, the associating of the electrocatalyst may help control the loading density of the electrocatalyst on the surface of the electrode. According to some embodiments, the tethering desirably allows control of the electrocatalyst via direct electronic connection via the at least partially base paired first and second oligo- or polynucleotides while additionally providing a distance between the electrocatalyst and the electrode. Such a distance from the electrode, in some embodiments, may increase mass transport of reactants to and products from the electrocatalyst, which may improve electrocatalytic performance. In some embodiments, despite a distance between the electrode and the electrocatalyst, the composition, article, or system comprising the electrocatalyst may be suitable for performing electrocatalysis. Without wishing to be bound by any particular theory, it is believed that the at least partially base paired (and in some cases fully base paired) first and second oligo- or polynucleotides provide sufficient electrical communication between the electrode and the electrocatalyst to perform electrocatalysis.

Some aspects are related to methods of making nanoparticles, e.g., copper nanoparticles. In some embodiments, the methods of making the nanoparticles are a bottom-up approach, which may be advantageous when compared to conventional top- down synthetic approaches. For example, conventional top-down approaches take synthesized copper nanoparticles and selectively etch certain particle surfaces to obtain a desired morphology. In contrast, the bottom-up methods disclosed herein, in some embodiments, synthesize nanoparticles having the desired morphology based on reagents present in the precursor solution, thereby desirably eliminating the need of an etching step as in conventional synthetic approaches. Additionally, in some embodiments, at least a portion of the composition of the nanoparticle may be advantageously controlled based on the selection of reagents present in the precursor solution, for instance, a reducing agent and/or a capping ligand. For example, in some embodiments, the presence of certain reducing agents and/or capping ligands, as described below, may desirably result in copper nanoparticles having an exterior surface that has a certain set of exposed lattice planes, low amount of copper oxide and/or is substantially free of copper oxide and/or is essentially free of copper oxide.

The methods described herein may include mixing a solution, for instance, mixing a precursor solution, in some embodiments. According to some embodiments, mixing may include by any of a variety of suitable mechanisms, for example, stirring, sonicating, shaking, vortexing, diffusion, or other appropriate forms of mixing. In some embodiments, the mixing may proceed for any suitable amount of time to ensure mixing of various components of the precursor solution as described below. In some embodiments, the solution may be mixed for greater than or equal to 30 seconds, greater than or equal to 1 minute, greater than or equal to 5 minutes, greater than or equal to 20 minutes, greater than or equal to 40 minutes, greater than or equal to 1 hour, greater than or equal to 2 hours, greater than or equal to 3 hours, greater than or equal to 4 hours, greater than or equal to 5 hours, greater than or equal to 6 hours, greater than or equal to 7 hours, greater than or equal to 8 hours, or greater than or equal to 10 hours. In some embodiments, the solution may be mixed for less than or equal to 12 hours, less than or equal to 10 hours, less than or equal to 8 hours, less than or equal to 7 hours, less than or equal to 6 hours, less than or equal to 5 hours, less than or equal to 4 hours, less than or equal to 3 hours, less than or equal to 2 hours, less than or equal to 1 hour, less than or equal to 40 minutes, less than or equal to 20 minutes, less than or equal to 5 minutes, or less than or equal to 1 minute. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 30 seconds and less than or equal to 12 hours, greater than or equal to 4 hours and less than or equal to 8 hours, greater than or equal to 5 hours and less than or equal to 7 hours). Other ranges are also possible.

In some embodiments, the solution that is mixed may be heated, for example, while contained within a container. Heating the solution may proceed through any of a variety of suitable methods, in accordance with some embodiments. Non-limiting examples of heating methods include heating the solution in an oil bath, an oven, using a resistive heating element, over an open flame, or any other suitable method for heating a solution. The heating of the solution may occur before, after, and/or simultaneous to the mixing of the solution. In some embodiments, the solution may be heated to an average temperature of greater than or equal to 20 degrees C, greater than or equal to 30 degrees C, greater than or equal to, 40 degrees C, greater than or equal to 50 degrees C, greater than or equal to 60 degrees C, greater than or equal to 70 degrees C, greater than or equal to 80 degrees C, or greater than or equal to 90 degrees C. In some embodiments, the solution may be heated to an average temperature of less than or equal to 100 degrees C, less than or equal to 90 degrees C, less than or equal to 80 degrees C, less than or equal to 70 degrees C, less than or equal to 60 degrees C, less than or equal to 50 degrees C, less than or equal to 40 degrees C, or less than or equal to 30 degrees C. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 10 degrees C and less than or equal to 100 degrees, greater than or equal to 50 degrees C and less than or equal to 70 degrees, greater than or equal to 80 degrees C and less than or equal to 100 degrees). Other ranges are also possible.

In some embodiments, a solution containing any of a variety of reagents may be mixed to form a precursor solution from which the nanoparticles may be formed. In some embodiments, various reagents may be contained within a solution, for example, an aqueous or a non-aqueous solution. According to some embodiments, the solution containing the various reagents comprises an aqueous solvent such as water. In some embodiments, the solution containing the various reagents comprises a non-aqueous solvent, such as one or more of chloroform, dichloromethane, ethanol, acetone, hexanes, and/or acetonitrile. Other solvents within the solution are also possible.

In some embodiments, suitable reagents that may be contained within the solution may include a reducing agent, a capping ligand, and/or a copper salt.

In some embodiments, the copper salt may include copper(I) and/or copper (II). Any of a variety of anions may be suitable for use in the copper salt, in accordance with some embodiments. The identity and/or concentration of the anion of the copper salt may be related to the resulting shape of the synthesized particles. Without wishing to be bound by any particular theory, it is believed that certain anions selectively adsorb to certain surfaces (e.g., lattice planes) of the nanoparticle during synthesis, which may direct the growth of the nanoparticle and at least partially determine the shape of the nanoparticle. In some embodiments, the copper salt is a copper halide. That is, in some embodiments, the anion of the copper salt is a halide. Halides include fluoride, chloride, bromide, and iodide. According to some embodiments, the copper salt is copper(II) bromide or copper(II) chloride.

According to some embodiments, a reducing agent may be included as a reagent within the solution. In some embodiments, the reducing agent comprises a sugar, e.g., a monosaccharide and/or a disaccharide. In some embodiments, the reducing agent is a monosaccharide and/or a disaccharide. In some such embodiments, the monosaccharide and/or the disaccharide include one or more of glucose, sucrose, fructose, ribose, lactose, and/or galactose. Other monosaccharides and/or the disaccharides are also possible as the reducing agent. According to some embodiments, other reducing agents are also possible, as this disclosure is not so limited. In some embodiments, the capping ligand of the reagents is an organic molecule. In some such embodiments, the organic molecule includes an amine. According to some embodiment, the capping ligand comprises or is hexadecyl amine, octadecyl amine, and/or oleyl amine. In some embodiments, the capping ligand comprises or is hexadecyl amine. In some embodiments, when mixing the solution, the reducing agent may reduce copper ions in solution to copper metal, whereafter a capping ligand associate with the copper metal to may decrease and/or prevent the amount of copper metal from being susceptible to further oxidation (e.g., to CuO). According to some embodiments, when the capping ligand comprises or is hexadecyl amine, the amount of CuO present in the resulting particles is decreases and/or the surface of the resulting copper nanoparticles is substantially free of CuO, e.g., in comparison to copper nanoparticles synthesized using a different capping ligand.

The pH of the solution in which the copper nanoparticle is synthesized may be any of a variety of suitable levels. In some embodiments, the pH of the solution is greater than or equal to 7, greater than or equal to 8, greater than or equal to 9, or greater than or equal to 10. According to some embodiments, the pH of the solution is less than or equal to 11, less than or equal to 10, less than or equal to 9, or less than or equal to 8. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 7 and less than or equal to 11). Other ranges are possible. In some embodiments, it may be desirable to increase the temperature of the reaction when using lower pH solutions (e.g., pH 7 vs pH 11), as the reduction of the Cu ions to copper nanoparticles may be facilitated in this manner.

Each of the reagents (e.g., copper salt, reducing agent, and/or capping ligand) may independently be present in the solution in any of a variety of concentrations, in some embodiments. According to some embodiments, each of the reagents may independently be present in solution in an amount of greater than or equal to 1 mg, greater than or equal to 5 mg, greater than or equal to 10 mg, greater than or equal to 20 mg, greater than or equal to 30 mg, greater than or equal to 40 mg, greater than or equal to 50 mg, greater than or equal to 75 mg, greater than or equal to 100 mg, greater than or equal to 150 mg, greater than or equal to 200 mg, greater than or equal to 250 mg, greater than or equal to 300 mg, greater than or equal to 350 mg, greater than or equal to 400 mg, greater than or equal to 450 mg, greater than or equal to 500 mg, greater than or equal to 600 mg, greater than or equal to 700 mg, greater than or equal to 800 mg, or greater than or equal to 900 mg per 100 mL of solvent. In some embodiments, each of the reagents may independently be present in solution in an amount of less than or equal to 1 g, less than or equal to 900 mg, less than or equal to 800 mg, less than or equal to 700 mg, less than or equal to 600 mg, less than or equal to 500 mg, less than or equal to

450 mg, less than or equal to 400 mg, less than or equal to 350 mg, less than or equal to

300 mg, less than or equal to 250 mg, less than or equal to 200 mg, less than or equal to

150 mg, less than or equal to 100 mg, less than or equal to 75 mg, less than or equal to

50 mg, less than or equal to 40 mg, less than or equal to 30 mg, less than or equal to 20 mg, less than or equal to 10 mg, or less than or equal to 5 mg per 100 mL of solution. Combinations of the foregoing ranges are possible (e.g., greater than or equal to 1 mg and less than or equal to 1 g per 100 mL of solution). Other ranges are also possible.

In accordance with some embodiments, the copper nanoparticles may be synthesized in a solution including a non-aqueous solvent. Accordingly, in some embodiments, the copper nanoparticles may then be washed, and the solvent exchanged to obtain the copper nanoparticles within an aqueous solution. For example, the solution including the nanoparticles and the non-aqueous solvent may be vortexed in a centrifuge, whereafter the supernatant (e.g., containing most of the non-aqueous solvent) may be removed and a pellet containing the nanoparticles is retained, according to some embodiments. An aqueous solution may then be added to the pellet to redistribute the nanoparticles therein, in some embodiments. This solvent exchange process may be repeated multiple times to obtain the copper nanoparticles in an aqueous solution and/or substantially free the non-aqueous solvent in which the nanoparticles were synthesized, in some embodiments.

Synthesizing the copper nanoparticles using the above-described bottom up approach may be desirable for number of reasons. For instance, as described above, the bottom-up approach may be more efficient by removing an etching step necessary in conventional top down approaches and/or may allow for the directed synthesis of the copper nanoparticles (e.g., to certain desirable shapes). Moreover, in some environments, the reagents used in the bottom-up approach described herein may decrease the cost of synthesizing the copper nanoparticles, compared to reagents used to produce conventional nanoparticles. Still other benefits include accessing certain shapes of nanoparticles that may be desirable or a flexibility to adjust the initial solution parameters to adjust the composition of the resulting nanoparticles.

Some aspects are generally directed to methods of making the articles and systems described herein. In some embodiments, electrocatalysts (e.g., nanoparticles) may be provided. For example, in some embodiments, the copper nanoparticles (e.g., or other catalysts) may be provided. It will be understood that while the methods of making articles or systems described herein are described in the context of copper nanoparticles, this is done for the sake of simplicity and other catalysts may similarly be used in place of the copper nanoparticles. Providing the copper nanoparticles may comprise synthesizing the copper nanoparticles, e.g., as described above, according to some embodiments. In some embodiments, copper nanoparticles may be acquired from a commercial source. In some embodiments, the copper nanoparticles may then be bound to a linker. In some embodiments, the linker comprises or is an oligo- or polynucleotide. Accordingly, in some embodiments, the copper nanoparticles may be bound to an oligo- or polynucleotide (e.g., a second oligo- or polynucleotide). In one set of embodiments, binding the linker to the copper nanoparticle includes forming a dative bond therebetween.

The method may include exposing the copper nanoparticles bound to the oligo- or polynucleotides to an electrode chemically bound to a first oligo- or polynucleotide, at least partially complementary to the oligo- or polynucleotide bound to the copper nanoparticle (e.g., the second oligo- or polynucleotide). In some embodiments, exposing the electrode to the copper nanoparticle comprises associating the first and second oligo- or polynucleotide of the electrode and copper nanoparticle, respectively. In some embodiments, the associating of the first and second oligo- or polynucleotide comprises the first and second oligo- or polynucleotides at least partially base pairing. Accordingly, in some embodiments, the method may comprise providing the electrode bound to a first oligo- or polynucleotide. In some embodiments, providing the electrode may comprise chemically binding the first oligo- or polynucleotide to the electrode. In some embodiments, the method includes exposing a solution containing the copper nanoparticle bound to the second oligo- or polynucleotide to a surface of an electrode to which the first oligo- or polynucleotide is bound and letting the first and second oligo- or polynucleotides at least partially base pair. In some embodiments, the method further comprises incorporating the article into a system, for example, a system configured for electrocatalysis. In some embodiments, the electrocatalysis is electrocatalytic CO2 reduction. Accordingly, in some embodiments, the method may further comprise electrocatalytically reducing CO2 using the article in the system. In some embodiments, the method may include performing electrocatalysis using an electrocatalysts (e.g., copper nanoparticles, or the like as described in more detail elsewhere herein).

FIG. 1C shows a non-limiting example of a method of making an article as described herein. In this example, an electrode 110 is chemically bound to a first oligonucleotide 120. The electrode 110 is exposed to an electrocatalyst 130 bound to a second oligonucleotide 122, allowing the first and second oligonucleotides 120 and 122 to at least partially base pair to form a double stranded oligonucleotide 124, thereby creating an article 100 where the electrode 110 and electrocatalyst 130 are associated together via the base paired oligonucleotides 120 and 122. In this instance, the electrocatalyst 130 is proximate the electrode 110.

In accordance with some embodiments, the copper nanoparticles described herein may be used in a variety of suitable applications. For example, it may be desirable to use the copper nanoparticles and electrocatalytic applications. In some embodiments, the copper nanoparticles may be dispersed (e.g., washed and/or resuspended) within a solution. In some such embodiments, the solution may contain a binder and/or conductive substance (e.g., carbon black, etc.) such that the solution may be deposited onto an electrode and the copper nanoparticles may be configured for electrocatalysis. In some embodiments, the copper nanoparticles may be used for thermal catalysis. Still other uses are possible.

According to some embodiments, the method may comprise disposing the copper nanoparticles proximate an electrode surface. In some embodiments, the copper nanoparticles may be bound to an oligo- or polynucleotide (e.g., a second oligo- or polynucleotide), which is in turn complementary and/or base paired to a first oligo- or polynucleotide chemically bound to the electrode. In some embodiments, an electrode chemically bound to the first oligo- or polynucleotide and is base paired to the second oligo- or polynucleotide bound to the copper nanoparticle (e.g., an electrode tethered to a copper nanoparticle) may be used for electrocatalytic applications. In some embodiments, the electrode tethered to a copper nanoparticle may be incorporated into a system configured for electrocatalysis (e.g., CO2 reduction). In some embodiments, the method may comprise electrocatalytically reducing CO2 using the electrode tethered to a copper nanoparticle. It will be understood how to perform electrocatalysis, for instance, by applying a current or voltage to an electrode in any suitable waveform and magnitude to achieve electrolysis of a reactant to form a desirable reaction product.

While the above is described generally in the context of copper nanoparticles, it should be understood that other electrocatalytic reactions may be selected and/or performed using the systems and methods described herein based on the identity of the catalyst.

The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.

EXAMPLE 1

The following Example describes a bottom-up synthesis method for copper nanoparticles.

Factors that Affect the Morphology of Copper-based Nanoparticles

Conventionally, spherical copper-based nanoparticles are synthesized and are then etched through top-down approaches to obtain copper nanoparticles having shapes other than spheres. Such top-down approaches include two steps, synthesizing the spherical particles and then etching the particles. In some such cases, the reagents used to synthesize these spherical particles and/or to etch the nanoparticles may be expensive.

In contrast, in this example, copper-based nanoparticles were synthesized through bottom-up wet chemistry with various precursors and sugars, in the presence and absence of hexadecylamine. The presence and/or absence of various reagents was shown to provide shape control when synthesizing the copper nanoparticles, thereby eliminating the need of the time-consuming etching process as in conventional methods. Additionally, avoiding the etching step and using the reagents described herein decreased the costs of making the copper nanoparticles when compared to conventionally processed nanoparticles. Finally, as described below in more detail, the bottom-up approach facilitated the formation of copper nanoparticles having different shapes and/or compositions (e.g., little to no copper oxide) than conventionally synthesized copper nanoparticles.

Samples were characterized using scanning electron microscopy (SEM) to determine the shape and size distribution of the copper nanoparticles as well as to confirm any impurities remaining after washing. X-ray diffraction (XRD) was additionally used to determine the oxidation state of the copper of the nanoparticles and dominant facets present in the nanoparticles and to correspondingly control the selectivity of the products produced during electrocatalysis.

Results show that hexadecylamine affected the oxidation state of the copper. Experiments done with hexadecylamine present in the precursor solution resulted in the precursor copper ions being reduced to copper metal as shown in the FIGS. 2A and 2B. When done in the absence of hexadecylamine at different pH values and temperature, precursor ions were reduced to a copper I or copper II-oxide based catalyst, examples of which are shown in FIGS. 2C and 2D. Note that the ability of the sugars to reduce copper ions in a variety of pH values at various temperatures to copper oxide, as show in FIGS. 2C and 2D, suggests that hexadecylamine plays an important role in kinetic control for the crystallization of copper metal nanoparticles.

While hexadecylamine is an important factor when synthesizing copper metal NPs or copper-oxide NPs, it was observed that the concentration of the anion in the precursor solution to affect the morphology of copper NPs. Various morphologies such as wires, rods, cubes, and spheres were observed when various sugars were reduced under a solution with copper chloride. When the concentration of [C1-] was increased by a factor of 2x and 4x of the concentration of copper ions from the addition of sodium chloride, the resulting samples consisted of all wires. In the case of copper bromide, the anion preference for the (110) facet was much stronger. The samples using copper bromide as precursor with different sugars resulted in all triangular sheet-like morphology as shown in the SEM image in FIG. 2A. The XRD spectrum corresponding to FIG. 2A confirms that the copper nanoparticles are metallic NP with a dominating (110) facet peak compared to other facets.

Without wishing to be bound by any particular theory, it is believed that the anion in solution forms a complex with the copper ions in the solution. After forming such complexes, it is believed that the different anions preferentially bind to different facets of the nanoparticle during synthesis (e.g., following initial reduction and/or during growth), allowing for control the desired morphology of the copper NPs during the reaction period.

While a sugar has a less significant effect, when chloride was the anion in solution, the sugar was shown to affect the resulting nanoparticles. Glucose and sucrose produced mostly wires and cubes, fructose was mainly wires and rods, while ribose and lactose did not lead to a nanoparticle distribution having a majority shape. Without wishing to be bound by any particular theory, it is believed that the shape control is due to thermodynamic and kinetic factors. For example, it is believed that the difference in energy needed to reduce monosaccharides and disaccharides due to breaking the glycosidic bond for disaccharides before it can be reduced affects the time needed for the reaction to go to completion. While sugar identity does not have a large effect in copper bromide solutions, ribose has been shown to increase growth along the (111) facet resulting in a triangular plate-like morphology.

Advantageously, the cost of the reagents (e.g., copper salts, sugars) is low and by using the bottom up method, post processing work such as etching from top down can be eliminated thus minimizing time, resources, and risks of oxidation. Copper bromide samples can be directly used in catalysis after washing since the distribution was almost all triangular- sheets due to the strong anion preference. One example usage would be in the electrocatalytic reduction of CO2 in which different facets on the copper NPs produce different products, and the copper bromide samples with dominating (110) facets will produce methane.

Purification of Copper Nanoparticles

Hexadecylamine (HD A) was used as a capping ligand for the synthesis of copper nanoparticles. The chemical properties of hexadecylamine allowed itself to be attached to the surface of the copper nanoparticles, which altered the growth rate of different facets and provided shape control of the nanoparticle during synthesis. However, it is beneficial to remove the hexadecylamine after the synthesis of the nanoparticles to provide an uncapped copper surface for certain surface science applications where an exposed copper surface is desirable, for example, electrocatalysis.

Copper nanoparticles were dispersed in milliQ water, reagent alcohol or ethyl acetate and were subsequently centrifuged. The supernatant following centrifugation was then removed to remove excess precursors and HDA therein. Samples were characterized using SEM and FTIR to analyze the effectiveness of HDA removal of each solvent, shown in FIG. 2E. The results showed that ethyl acetate was the most effective solvent for removing excess precursor components and the HDA from the copper nanoparticles. From the SEM images obtained, there are substantially no impurities on the surfaces of the copper nanoparticle purified using ethyl acetate. In contrast, samples purified with milliQ water and reagent alcohol both have some amount of impurities on the surfaces of the CuNPs.

Additional examples are shown in FIG. 2F, which shows images of copper nanoparticles samples washed in different solvents.

Catalysis

A potential application of shape-controlled copper nanoparticles is using it as an electrocatalyst to produce common reductions products like methane, ethylene, and ethanol from carbon dioxide. Different shapes of the copper nanoparticles samples were dispersed on carbon paper to catalyze carbon dioxide reduction, and products obtained were quantified using gas chromatography to analyze the performance and selectivity of the CuNP catalyst. Results confirm that different shapes of CuNPs exhibited different selectivity towards a certain product.

The reported results show the potential of using copper nanoparticles as an electrocatalyst for the production of common reduction products. The CuNP samples synthesized for CO2 reduction all consist of a mixture of shapes. Notably, CuNPs produced from CuBr2 mostly include a triangular morphology. This may be desirable as, without wishing to be bound by any particular theory, nanoparticles having different shapes and different surfaces exhibit different selectivity towards reaction products, facilitating the ability to select the desired reaction product distribution.

EXAMPLE 2

The following Example describes DNA-directed immobilization of molecular catalyst for the electrochemical reduction of carbon dioxide.

Electrochemical reduction of carbon dioxide (CO2) is a promising route to up- convert this industrial by-product. However, to perform this reaction with a smallmolecule catalyst, the catalyst must be proximal to an electrode surface. Efforts to immobilize molecular catalysts on electrodes have been stymied by the need to improve immobilization chemistries on a case-by- case basis. Taking inspiration from nature, DNA was applied as a molecular-scale “Velcro” to tether three porphyrin-based catalysts to electrodes. This tethering strategy improved both the stability of the catalysts and their Faradaic efficiency (FE). DNA-catalyst conjugates were immobilized on screen-printed carbon electrodes and carbon paper electrodes via DNA hybridization with nearly 100% efficiency. Following immobilization, higher catalyst stability at relevant potentials is observed. Additionally, lower overpotentials are required for CO generation. Finally, high Faradaic efficiency (FE) for CO generation was observed with the DNA- immobilized catalysts as compared to the unmodified small-molecule systems, as high as 79.1% FE for CO at -1.15 V using a DNA-tethered catalyst. This example demonstrates the potential of DNA “Velcro” as a powerful strategy for catalyst immobilization, while further showing improved catalytic characteristics of molecular catalysts for CO2 valorization.

An expected 500 gigatons of carbon dioxide (CO2) will be produced in the next five decades as a major by-product of industrial processes. Despite its abundance and potential as a one-carbon feedstock, CO2 has yet to be extensively used to generate value-added chemicals. The first step in this process is the reduction of CO2 to generate carbon monoxide (CO), a key component of synthetic gas (syngas) which is used as a fuel source and as an intermediate for chemical production. Thus, significant effort has been devoted to the development of technologies to convert CO2 to CO. Electrochemical CO2 reduction (CO2 reduction reaction — CO2RR) is one of the most common methods of CO2 conversion, with many examples of both homogeneous and heterogeneous systems. Small-molecule catalysts for CO2RR are advantageous because of their tunability and well-defined active sites. These catalysts can be employed homogeneously, but their immobilization on electrodes is advantageous, as it can improve catalyst-electrode interactions. In heterogeneous systems, both the local environment surrounding the catalyst and the ability of the reactant to reach the active site significantly impact the conversion efficiency and reaction products.

Synthetic catalysts promise tunability and scalability, but enzymes (e.g., native protein catalysts) often outperform these small molecules because of their substrate specificity and ability to both activate the reactant and stabilize the reaction intermediate. One example active site found in many enzymes is porphyrin, a ligand structure that often chelates cobalt or iron (FIG. 3A). This moiety is found in enzymes ranging from oxygenases to peroxidases and is the core of engineered cytochromes capable of complex transformations including C-H activation. Thus, this biological molecule was selected in this example to improve CO2RR. Conventionally, using porphyrin-derived ligand structures, molecular catalysts have been shown to perform CO2RR, although their efficiency remains relatively low compared to other catalysts.

One strategy to improve catalysis is to immobilize small molecules on electrode surfaces, either through direct grafting of a ligand to the electrode or by non-covalent interactions between pyrene moieties appended to ligands and low-dimensional carbon surfaces. However, these systems limit the conformational flexibility of the catalyst, constrain transport of the reactant to the catalytic center, are often limited by solubility, and yield current densities lower than their homogeneous equivalents. It was desirable to improve heterogeneous catalysis with these small molecules using the chemical properties of DNA (FIG. 3A); because of its stability, chemical tunability, and inherent self-recognition, DNA was selected to serve as a generalizable platform for catalyst immobilization. The self-recognition of DNA, due to hydrogen bonding between proper base pairs, provides a sequence-specific, non-covalent adhesive mechanism for controlled surface attachment. Therefore, DNA was used as a “molecular Velcro” to immobilize porphyrin-based CO2RR catalysts.

DNA is often thought of solely in the context of the genetic code, but its three- dimensional structure imbues it with unique materials properties beyond this role. DNA is a naturally- occurring polymer comprised of two complementary oligonucleotide strands. These strands self-recognize through base-pair hydrogen bonding, serving as sequence-specific “Velcro.” Further, once the DNA duplex is formed, the pi orbitals of the aromatic bases overlap to stabilize the structure of DNA. Despite these advantages, DNA has yet been applied to energy- relevant catalysis. Here, we demonstrate the first application of DNA “Velcro” to immobilize molecular CO2RR catalysts on electrode surfaces (FIG. 3B). The DNA-catalyst conjugates of this example are readily synthesized and have improved stability as compared to the small-molecule catalysts alone simply through the incorporation of the DNA. Subsequent immobilization of the DNA-catalyst conjugates on carbon electrodes through hybridization to pre-deposited complementary DNA strands showed improved Faradaic efficiency of the catalyst toward CO production.

Results and Discussion

Catalyst selection and synthesis

Based on their similarity to enzyme active sites, three porphyrin-based catalysts were selected for initial investigation: (Co(II) and Fe(III) tetrakis(4- carboxyphenyl)porphyrin (H2TCPP)— CoTCPP and FeTCPP, as well as hemin, FIG. 3C). These catalysts all have known catalytic properties, readily-understood mechanism of proton-coupled electron transfer (PCET), and ability to vary the metal incorporated into porphyrin derivatives. Commercial hemin with the iron incorporated was used, and CoTCPP and FeTCPP were metalated with the corresponding metal ions from commercial H2TCPP. Metalation was confirmed by mass spectrometry (FIG. 3D). Synthesis and optimization of DNA-catalyst conjugates

Enzymes are often highly susceptible to deactivation from temperature fluctuations, pH changes, and the relative ionic strength of the solution in which they are maintained. Further, proteins can be challenging to generate at scale without significant process optimization and costly purification. Thus, to improve the stability and system control, DNA was considered for incorporation into the system. Because DNA is highly stable under diverse aqueous conditions (e.g., a wide range of temperatures, pH’s, and ionic strengths), tunable, and synthetically tractable, it was chosen as an addition to molecular catalysts that suffer from aqueous solubility issues and limited stability.

To investigate the impact of DNA on CO2RR with the porphyrin- based catalysts, catalyst-oligonucleotide conjugates were synthesized, which were termed single- stranded DNA (ssDNA) conjugates. Traditional bioconjugation strategies were undertaken involving amide bond formation between the catalyst ligand containing carboxylic acids and amine-terminated ssDNA (FIG. 3E, which are UV-Vis spectra of single-stranded DNA 1 (ssDNA), H2TCPP, CoTCPP and CoTCPP-ssDNA conjugates in aqueous buffer). Porphyrin-DNA conjugates are known, but have mainly been used in fundamental scientific studies (e.g., for DNA sensing and inter-strand crosslinking). The relatively narrow range of applications to-date is attributed to challenging synthesis, intermolecular interactions that can lead to aggregation, and solubility issues. Indeed, prevalent amide coupling conditions (l-ethyl-3-(3- (dimethylamino )propyl)carbodiimide (EDC), 1 -hydroxybenzotriazole (HOBt) and DIPEA) and found no noticeable conversion with any of the three molecular catalysts. Therefore, a variety of prevalent reagents for amide bond formation were evaluated and it was found that most of the established reagents resulted in very low yields for this reaction. The highest yields were consistently found with a combination of hexafluorophosphate azabenzotriazole tetramethyl uronium and N,N’ -diisopropylethylamine (HATU/DIPEA) reagents, which provide decent conversion for all three ssDNA-catalyst conjugates. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and reverse phase high performance liquid chromatography (RP-HPLC) confirmed the successful synthesis and purification of the hemin- and Co/FeTCPP-DNA conjugates (FIGS. 3F-3G).

Despite the prevalence of this reaction for bioconjugations and the similarity of the core ligand structures for the three catalysts evaluated, significant differences were observed in the efficacy of standard reagents based on the catalyst being conjugated. Carbon surface modification with DNA

Prior to surface immobilization of the ssDNA-catalyst conjugates, electrodes stably modified with complementary DNA were needed. Conventionally, electrode modification with biomolecules is performed on gold surfaces due to their ease of modification with any biomolecule containing a free thiol. Despite this ease, gold surfaces of sufficient quality for modification are costly, the accessible potential window is smaller than that of other materials such as carbon, and the gold-thiol bond formed is relatively unstable and susceptible to reductive stripping (e.g., under conditions suitable for performing CO2RR). Thus, for the potentials required for CO2RR, gold was an unsuitable material. Accordingly, carbon electrodes were modified with biomolecules using an oxidative coupling bioconjugation reaction (FIG. 4A).

Preparation of aniline-modified electrodes for DNA conjugation was achieved by electrochemically-induced grafting of o- nitroaniline through the generation of a diazonium salt and subsequent reduction of the resultant nitrobenzyl at the surface to an aniline moiety (FIG. 4A). The successful electrode modification was confirmed by characteristic reductive peaks observed in the cyclic voltammogram (CV) (-0.05V vs AgCl/Ag, and -0.9 V vs AgCl/Ag respectively; FIG. 4B, which shows CVs of diazonium and nitrophenyl on SPE at a scan rate of 100 mV/s). Subsequent coupling of ssDNA to aniline-modified screen-printed electrodes (SPEs) was accomplished using the mild oxidant ferricyanide and o- aminophenol-modified DNA (FIG. 4C).

Successful coupling was validated by hexammineruthenium (RuHex) DNA quantification. RuHex interacts electrostatically with the DNA backbone to act as a phosphate counter (FIGS. 4D-4E; FIG. 4D shows CVs of ssDNA modified or uncoated SPE in a stock solution (10 mM Tris buffer, pH 7.4, containing 10 pM RuHex), carried out at a scan rate of 100 mV/s; FIG. 4E shows CVs of diazonium or nitrophenyl on SPEs taken at a scan rate of 20 mV/s). From these results, the surface concentration of oligonucleotides was calculated to be (7.2 ± 3.0) x 10-12 mol/cm² (FIG. 4E). This is well within the standard DNA coverages observed using conventional gold-thiol chemistries, which generally range from 1-100 pmol/cm². Thus, the maximum surface density of catalyst loading on the electrode following hybridization was 7.2 pmol/cm². To evaluate the efficacy of this modification on more conventional substrates for catalyst immobilization, the same protocol were performed on carbon paper to add ssDNA to the surface. Just as with the SPEs, the successful carbon paper modification was confirmed by a reductive peak observed in the CV (-0.1 V vs AgCl/Ag, and -0.95 V vs AgCl/Ag respectively; FIG. 4F). After coupling of ssDNA to aniline-modified carbon paper, the surface coverage of oligonucleotides was calculated to be 147 pmol/cm² (geometric surface area of carbon paper) by RuHex DNA quantification.

Confirmation of consistent carbon electrode modification with DNA, especially because low-cost SPEs and carbon paper electrodes were used in this study, was desirable to the success of immobilization of electrocatalysts on electrodes. DNA hybridization efficiency

Having successfully modified SPEs with ssDNA, DNA hybridization or “Velcro” efficiency to ssDNA-modified surfaces was examined. Both DNA-modified electrodes and complementary DNA-catalyst conjugates were heated to 65 °C. The ssDNA-catalyst conjugate was added to the complementary DNA-modified electrode. The electrode was then slowly cooled to room temperature over one hour, and the unbound catalyst-DNA conjugates were removed by repeated washing. Hybridization efficiency to the ssDNA electrode surface was evaluated by RuHex DNA quantification.

Impressively, the total charge obtained by integration of the redox peaks in the cyclic voltammograms was calculated to be 1.64 pC after catalyst-DNA hybridization, whereas the total charge from the ssDNA-modified SPE was determined to be 0.84 |aC (FIG. 4D). Thus, the surface density of catalyst is estimated to be 6.4 pmol/cm², achieving near-unity hybridization efficiency (the surface concentration of single-strand oligonucleotides on the SPE surface was calculated to be 6.5 pmol/cm²; detailed elsewhere herein). Moreover, in the presence of CO2, a ten-fold increase in current was observed by chronoamperometry for the catalyst-modified electrode in KCI/K2CO3 electrolyte as compared to the electrode modified only with ssDNA. These data indicate that the catalyst-DNA was successfully immobilized on the electrode through DNA hybridization and that the hybridization maintained the activity of the catalyst (FIG. 4G, which shows chrono amperometry of a ssDNA functionalized and dsDNA-CoTCPP modified screen-printed carbon electrode, carried out at -1.2 V vs SHE. The electrolyte is KC1 (0.1 M) and K2CO3 (0.5 M) at pH 7.4, adjusted by adding aliquots of HC1). This observation is important for the application of DNA hybridization at an electrode for catalysis, as altering the activity or accessibility of biomolecules on surfaces is often a concern following immobilization.

Stability of catalysts under relevant electrochemical conditions

Though TCPP-based catalysts are established for many energy- relevant transformations, one key challenge with their implementation is their instability. These and catalysts with similar ligand structures are prone to deactivation. Indeed, both CoTCPP and FeTCPP at -1.2 V vs RHE (the potential at which CO2RR occurs) show rapid decomposition. The significant change in current indicates that catalyst decomposition and, potentially, precipitation onto the electrode occurs in this electrochemical potential regime (FIG. 5A). Despite the instability of the TCPP catalysts, the current observed by chronoamperometry for hemin remains stable at -1.2 V vs RHE. Taken together, the chronoamperometry stability data confirm the observations for the ssDNA modification of these catalysts. When these homogeneous molecular catalysts are in solution, they are unstable at the requisite potential for CO2RR, making them unsuitable for this conversion at scale.

The challenges in optimizing coupling conditions highlight one of the key drawbacks of porphyrin derivatives: their limited solubility in aqueous buffers. Surprisingly, though, following DNA modification, improved aqueous solubility of the catalysts was observed. Thus, the impact of DNA addition to the catalysts in solution was investigated. The stability of the conjugates was evaluated, as well as their ability to perform CO2RR, without immobilization to the electrode. When compared to the largely insoluble small-molecule catalysts, the DNA conjugates were found to be highly soluble in aqueous buffers without the addition of co- solvents. This is a significant finding, as fully aqueous- soluble catalysts allow for additional flexibility in the pH and buffering conditions as well as the electrolyte that can be used with the system. Both of these variables significantly impact CO2RR efficiency independent of the catalyst, making the ability to tune these parameters without solubility concerns a significant advantage of our strategy. Given the results, a range of energy-relevant conversions could be improved through catalyst modification with DNA.

The DNA-modified hemin demonstrated similar stability to the unmodified version. Interestingly, the addition of DNA to the TCPP-derived catalysts provided an immediate and significant improvement in catalyst stability. Under the same electrochemical conditions as were used to evaluate the unmodified porphyrin catalysts, the DNA-modified catalysts maintained their activity and remained stable at potentials that caused degradation for the small-molecule catalysts alone (FIG. 5B, which shows chronoamperometry of DNA-modified catalyst in solution is CoTCPP (top), FeTCPP;(middle), and Hemin (bottom), carried out at -0.95 V, -1.2 V and -1.3 V vs SHE in carbon SPEs. The electrolyte is KC1 (0.1 M) and K2CO3 (0.5 M) at pH 7.4, adjusted by adding aliquots of HC1.). Thus, adding the soluble oligonucleotide significantly improved the stability of the catalysts in solution (FIG. 5A). Although solvent effects are known in CO2RR catalysis, this finding supports the impact of the local environment of the metal center on the stability of the small molecules, beyond simple pH and ionic effects. The next step was therefore to evaluate overall catalysis efficiency.

Surprisingly, for DNA-immobilized CoTCPP, steady currents were observed by chronoamperometry at low overpotentials (-0.95 V vs RHE), indicating that DNA “Velcro” leads to improved CO2RR catalyst stability (FIG. 5C, which are chronoamperograms of DNA-modified catalysts hybridized to the electrode surface, carried out at -0.95 V, -1.2 V and -1.3 V vs. SHE, CO2 flow rate: 10 seem. Experiments are performed on carbon SPEs, and the electrolyte used is KC1 (0.1 M) and K2CO3 (0.5 M) at pH 7.4, adjusted by adding aliquots of HC1.). Both FeTCPP and hemin immobilized with DNA showed stable currents at relevant potentials for CO2RR (- 1.2 V vs RHE), despite their homogeneous equivalents showing degradation at this potential (FIG. 5A). Impressively, the amount of CO generated from the pm/cm² of catalyst immobilized on the electrode is comparable to the amount generated from pM concentrations of homogenous catalyst in solution (FIG. 5D), which shows the analysis of in line gas chromatography. The CO flow rate analysis by free catalyst in solution (0.5 mM) and DNA-modified catalyst on electrode (6.5 pmol-cm’²) (CO2 flow rate: 10 seem), carried out at -1.3 V vs SHE on carbon SPEs. The electrolyte is KC1 (0.1 M) and K2CO3 (0.5 M) at pH 7.4, adjusted by adding aliquots of HC1.). The observation of CO by gas chromatography (GC) confirms that the catalyst center remains the active site on the electrode, as no CO production was observed for DNA-modified electrodes alone (FIG. 5E, which are plots obtained using in-line gas chromatography of bare electrode (carbon screen-printed electrode), carried out at -1.3 V vs SHE on carbon SPEs using the same electrolyte solution as in FIG. 5D. The bottom plot shows in-line gas chromatography of calibration gas tank).

CO2RR in solution with porphyrin-based, catalysts

CO2RR of these three porphyrin-derived catalysts in solution using SPEs in aqueous carbonate electrolyte was initially investigated because of their prevalence in CO2RR studies. Additionally, the free porphyrin-based catalysts are soluble in this class of solvents at the concentrations used herein. As seen in FIGS. 6A-6C, catalytic current is observed by cyclic voltammetry (CV) using 0.5 mM CoTCPP in aqueous carbonate electrolyte saturated with CO2 at neutral pH. In the absence of CO2, the observed current was three- fold lower than in its presence (-1.2 V vs. RHE, FIG. 6A). Similarly, the current generated by FeTCPP under the same conditions exhibited a two-fold increase when the buffer was saturated with CO2. Under an N2 atmosphere, three redox processes are observed. Peak A is attributed to the FeIII/II couple, while peaks B and C are attributed to the irreversible FeII/I reduction and hydrogen evolution, respectively, which is supported by prior literature characterization. The increase in current observed in the FeVO potential region (between -1.4 and -1.3V vs AgCl/Ag) when CO2 is present in the solution is indicative of CO2RR, which was later confirmed by gas chromatography.

In contrast to the TCPP-based catalysts, no significant difference in current was observed for 0.5 mM hemin in a 95% buffer/5% acetonitrile (ACN) solution either in the presence or absence of CO2 (FIG. 6C). The addition of ACN to the solvent for this catalyst is due to its limited solubility in aqueous electrolyte alone. The observation of equivalent current generation is explained by the inevitable competition between CO2 reduction and hydrogen evolution in aqueous buffers. Indeed, the results from the chromatographic analysis of the gaseous products generated in the headspace of the electrochemical cell indicate the CO production rates are relatively low with this catalyst (FIG. 5).

In order to accurately determine the efficiency of porphyrin-based smallmolecule catalysts for CO2RR in aqueous buffer, CoTCPP were tested in a customized two-compartment cell separated by an ion-exchange membrane to prevent platinum (Pt) crossover. A carbon paper working electrode and Pt foil counter electrode are used with this cell. Using an in-line gas chromatograph (GC), the Faradaic efficiencies (FEs) toward CO for CoTCPP-based catalysts were calculated to be 19.6%, 30.0%, and 10.9% at -0.95, -1.2 and -1.3 V vs. RHE (FIGS. 7A-7B), respectively.

Electrocatalysis improvements

Owing to low surface area of carbon SPEs, the products of CO2RR from the dsDNA-catalyst modified electrode are relatively low compared to the competing hydrogen evolution reaction based on our results from in-line GC. To accurately determine the Faradaic efficiency (FE) of the system, dsDNA-catalyst-modified carbon paper was tested as the working electrode in the custom cell (FIG. 7B). The CoTCPP- ssDNA conjugates were hybridized to the surface of carbon paper modified with complementary ssDNA. After RuHex quantification of the DNA on the surface was compared to the catalyst electrochemical signal (FIG. 7C), the surface density of catalyst was estimated to be 144 pmol/cm2 (geometric surface area of carbon paper), demonstrating a hybridization efficiency of over 98% (the surface concentration of single- strand oligonucleotides on carbon paper was calculated to be 147 pmol/cm², as described previously). For CoTCPP immobilized with DNA, CO2 electrocatalysis was observed at a less negative overpotential (- 0.95 V vs. RHE), and high selectivity toward CO formation was observed by GC with minimal hydrogen evolution in FIG. 7D, which shows the faradaic efficiency of CoTCPP immobilized with DNA toward CO (FE(CO)) is calculated to be 79.1%. This efficiency represents a 4-fold increase compared to the homogenous molecular catalysts (19.6%) (FIGS. 7A-7E). When applying a higher potential (-1.2V vs. RHE), the FE(CO) of the heterogenous system is 32.7%, higher than that of the homogenous system (30.0%). As expected, the hydrogen evolution competing reaction dominated for both systems when they were held at a more negative potential (- 1.3 V vs. RHE). The immobilization of ssDNA-catalyst conjugates on electrodes had the intended effect: improving FE while maintaining the improved stability observed with ssDNA-catalyst conjugates in solution.

Furthermore, buffer effect on the selectivity of CO2RR using catalyst-dsDNA immobilized carbon paper was evaluated. The sodium bicarbonate electrolyte at neutral pH has the highest selectivity toward CO relative to H2 formation (FIG. 7F). Taken together, these results demonstrate the circumvention of key challenges in CO2RR with small-molecule catalysts: stability and efficiency. Finally, the turnover frequency (TOF) was measured for each of the three catalysts under each DNA modification condition. For each catalyst, the free, small-molecule catalyst, the ssDNA-catalyst, and the DNA- immobilized catalyst are compared. As can be seen in FIG. 8, DNA-immobilized catalysts yielded TOFs at least an order of magnitude (for CoTCPP) and as high as three orders of magnitude (for FeTCPP and hemin) higher than free catalysts in solution. Thus, not only does the addition of DNA improve the stability and FE of the system, but DNA- immobilized catalyst also demonstrates significantly higher turnover rates.

The elegance of enzymatic reactions has inspired the incorporation of biomolecules such as amino acids and peptides with CO2RR catalysis to improve selectivity and solubility. In this example, the ability of DNA to serve as a molecular “Velcro” to tether porphyrin-based small-molecule CO2RR catalysts to electrodes was evaluated. For the metalloporphyrin catalysts employed in this example, the efficiency of CO2RR for the desired CO product is closely related to the microenvironment surrounding the metal centers. Without wishing to be bound by any particular theory, it is believed that the improved CO2RR efficiency observed in the system of this example is due to alterations in the outer coordination sphere resulting from the presence of DNA. Moreover, it was observed that, for DNA-immobilized CoTCPP, CO2RR could be carried out at a less negative potential than for the homogeneous catalysis (-0.95 V vs RHE), which is likely due to the increased stability and solvent accessibility of the catalyst.

Overall, DNA “Velcro” for tethering catalysts to electrodes was shown to improve catalytic efficiency and stability. The readily- synthesized catalyst-ssDNA conjugates afford improved aqueous solubility. Furthermore, the DNA hybridizationbased CO2RR catalyst immobilization yielded systems with higher TOF compared to the unmodified controls. Taken together, the results show DNA “Velcro” improve catalysis. Materials and. Methods

Functionalization of amino-modified DNAs with metalated TCPP catalyst by HATU/DIPEA method:

In a typical reaction, to a solution of amino-modified DNA (2.0 nmol) in MOPS buffer (300 pL, 50 mM, 0.5 M NaCl, pH 8.0) was added a mixture of FeTCPP (0.2 mg, 240 nmol), HATU (0.8 mg, 2.1 pmol), and DIPEA (0.4 pL, 2.1 pmol) in 300 pL DMF at room temperature. The reaction was agitated for 24 hours and resulted in covalent attachment of the FeTCPP complex to the DNA. The DNA-catalyst conjugates were then purified by reverse-phase HPLC using a water (50 mM TEAA) (solvent A)/ACN (solvent B) gradient and characterized by MALDI-TOF mass spectrometry. Chemicals and Reagents.

All chemicals were reagent grade and used without further purification unless otherwise stated. Iron (III) chloride (FeC13, 97%), cobalt (II) acetate tetrahydrate, potassium hexacyanoferrate (III) (99%), hexaammineruthenium (III) chloride (98%), pentacarbonylchlororhenium (I) (98%), bromopentacarbonylmanganese (I), 4, 4’, 4”, 4”’- (porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (H2TCPP, 75%), hexafluorophosphate azabenzotriazole tetramethyl uranium (HATU, 97%),N-(3- dimethylaminopropyl)-N’ -ethylcarbodiimide hydrochloride (EDC, commercial grade), N, N-diisopropylethylamine (DIPEA, 99%), 4-nitroaniline (99%), sodium nitrite (97%), ammonium citrate dibasic (98%), 3-hydroxypicolinic acid (99%), chloroform-d (99.8%), sodium hydrosulfite (technical grade), sodium hydroxide (98%), hydrochloride acid (37%), potassium carbonate (99%), potassium chloride (99%), sodium phosphate dibasic (99%), sodium phosphate monobasic (99%), and were purchased from Sigma- Aldrich. Sodium chloride, acetonitrile (HPLC grade) and absolute ethanol (molecular biology grade) were purchased from Fisher Scientific. 1 -hydroxybenzotriazole monohydrate (HOBt, 97%) was purchased from TCI America. 2.0 M triethylamine acetate buffer (TEAA, HPLC grade) was purchased from Applied Biosystems (Thermo Fisher Scientific). Hemin (porcine, 97%) and N, N-dimethylformamide (anhydrous DMF, 99.8%) were purchased from Alfa Aesar. Ultrapure water was generated from an ELGA PURELAB Quest UV (Model number: PQDIUVM1NSP). Synthetic oligonucleotides were produced by Integrated DNA Technologies, Inc or Sigma- Aldrich. The following sequences were used: (1) 5'-/5AmMC6/CA CAC ACA CAC ACA CAC ACA -3' - (ssDNA for the synthesis of DNA-catalyst conjugates); (2) 5'-/5AmMC6/-TGT GTG TGT GTG TGT GTG TG -3' (Complementary ssDNA for the synthesis of o- aminophenol-DNA conjugates).

Analysis and. Measurement.

Mass spectra were measured on a nominal mass Agilent 6125B mass spectrometer with electrospray (ESI) ionization attached to an Agilent 1260 Infinity LC (LC-MS) or on a high resolution Bruker Autoflex LRF Speed mass spectrometer with 3-hydroxypicolinic acid (3-HPA) for DNA as a matrix (positive ion mode). UV- Visible spectra were measured on a NanoDrop™ One Microvolume UV-Vis Spectrophotometer (Thermo Scientific, USA). The oven temperature was set to 85 °C throughout the experiments. CO2 was continuously flown through the electrochemical cell, and the on-line gas chromatography (GC) with a Hayesep-D column was used to measure products periodically. Small molecules like H2 and CO elute from the column very quickly without much separation. A thermal conductivity detector (TCD) was used to measure H2, and a flame ionization detector (FID) with a methanizer was used to detect all carbonaceous products. For the experiments conducted using a sandwich-type cell, a different GC configuration was used. An auto-sampled gas flow was first sent onto a 6’ Hayesep-D pre-column, and then flowed onto a 3’ MS-5 A column, while back-flushing the pre-column before CO2 elutes. At the same time, another sample was collected and held without flowing. After light components including hydrogen D column, while H2 was quantified after being eluted from MS-5A column. The electrochemical measurements were performed on either a Gamry Ref 600 potentiostat/galvanostat (Gamry Instruments Inc, USA) or a Biologic VMP300 multi-channel potentiostat/galvanostat (Biologic, France). All measurements were made versus a silver chloride/silver (AgCl/Ag) reference (CH Instruments, USA) and a Pt counter electrode. Conversion from AgCl/Ag to RHE was performed through calibration using standard protocols.

Metal complex, DNA-catalyst, and DNA- aminophenol Conjugates Synthesis. (1) Metalation of H2TCPP'. Generally, a solution of H2TCPP (32.0 mg, 0.04 mmol) in 10 mL of DMF was added to a solution of iron chloride (80.0 mg, 0.49 mmol) in DMF (10 mL). The mixture was refluxed for 2 h under N2 and then cooled to ambient temperature. After solvent removal by rotary evaporation, the mixture was re-suspended in 0.1 M NaOH, and the metalation product was precipitated from solution upon gradual addition of 0.1 M HC1. Precipitation was repeated three times, and the product was dried overnight under reduced pressure (yield: 84.7%). The metalation product was characterized by UV-Vis spectrophotometer and LC-MS or MALDLTOF mass spectrometry.

(2) Functionalization of amine-modified DNAs with metalated TCPP using HATU/D1PEA'. In a typical reaction, to a solution of amine-modified DNA (2.0 nmol) in MOPS buffer (300 pL, 50 mM, 0.5 M NaCl, pH 8.0) was added a mixture of FeTCPP (0.2 mg, 240 nmol), HATU (0.8 mg, 2.1 pmol), and DIPEA (0.4 pL, 2.1 pmol) in 300 pL DMF at ambient temperature. The reaction was agitated for 24 h and resulted in covalent attachment of the FeTCPP complex to the DNA. The DNA-catalyst conjugates were then purified by reverse-phase HPLC using a water (50mM TEAA) (solvent A)/ACN (solvent B) gradient and characterized by MALDLTOF mass spectrometry.

(3) Functionalization of amine-modified DNA with o-nitrophenol NHS ester (1): The onitrophenol NHS ester was synthesized as previously reported.Sl 11.16 mg (36 pmol) of onitrophenol NHS ester was dissolved in 1 mL of DMF to make a 36 mM stock solution. 200 pL of the stock solution was then added to the amine-modified DNA stock solution (60 nmol, 200 pL of 50mM phosphate buffer, pH 8.0). The color of the solution turned orange. The reaction was agitated at ambient temperature for 90 minutes. The resulting solution was passed through a 0.22 pm filter, and the filtrate was purified by NAP-5 column (General Electric, USA) and analyzed by MALDLTOF mass spectrometry.

(4) Synthesis of o-aminophenol DNA (2): The purified compound 1 (o-nitrophenol-DNA conjugates) solution (1 mL) was subsequently reduced by addition of sodium hydrosulfite (1.74 mg, 0.01 mmol in 200mM phosphate buffer, pH 6.5). After addition, the yellowish solutions immediately turned colorless. The reaction was agitated at ambient temperature for 20 mins and purified by using a NAP- 10 column (General Electric, USA) and analyzed by MALDLTOF mass spectrometry. (5) Functionalization of amino-modified DNAs with metalated TCPP catalyst by HATU/D1PEA method'. In a typical reaction, to a solution of amino-modified DNA (2.0 nmol) in MOPS buffer (300 pL, 50 mM, 0.5 M NaCl, pH 8.0) was added a mixture of FeTCPP (0.2 mg, 240 nmol), HATU (0.8 mg, 2.1 pmol), and DIPEA (0.4 pL, 2.1 pmol) in 300 pL DMF at ambient temperature. The reaction was agitated for 24 hours and resulted in covalent attachment of the FeTCPP complex to the DNA. The DNA-catalyst conjugates were then purified by reverse-phase HPEC using a water (50 mM TEAA) (solvent A)/ACN (solvent B) gradient and characterized by MAEDI-TOF mass spectrometry.

Carbon Electrode Modification.

(1) p-nitrophenyl diazonium-functionalized electrodes'. 300 pF of p-nitroanilinc stock (50 mMin ACN) was added to 15 mF 4% (v/v) HC1 solution. After degassing with N2 in ice water bath for 15 mins, 300 pF of a sodium nitrite (100 mM in water) stock solution was added dropwise to the reaction mixture while stirring. The reaction was kept for 5 mins, and a glassy carbon electrode or screen-printed carbon electrode (SPE), not previously assembled with p-nitrophenyl diazonium, was immersed in solution. Two cyclic voltammogram cycles were run on the carbon electrode from 600 to -200 mV vs. AgCl/Ag, at 100 mV-s-1. The modified electrode was then washed with water and briefly dried under a stream of N2.

(2) reduction of nitrophenyl to aniline'. A 0.1 M KC1 water/ethanol solution was prepared by adding 372.75 mg KC1 to 45 mF water and 5 mF ethanol. 10 mF of above stock solution was transferred into a 20 mF vial, and degassing with N2 for 15 mins. A carbon electrode functionalized with p-nitrophenyl was then immersed in the solution and two cyclic voltammogram cycles were run from -300 to -1300 mV vs. AgCl/Ag, at 100 mV. The modified electrode was then washed with water and briefly dried under a stream of N₂.

(3) oxidative coupling reaction of aniline with o-aminophenol DNA conjugates: The purified compound 2 (o-aminophenol DNA conjugate) was dissolved in phosphate buffer (100 mM, pH 6.5) to make a 100 pM DNA stock solution. 2 pF of potassium ferricyanide stock (100 mM) was added to 20 pF of the DNA stock solution. The mixed solution was subsequently drop-cast onto the aminophenol-functionalized carbon electrode, and the oxidative coupling reaction was kept in a humidified box overnight. The modified electrode was then washed with phosphate buffer (5 mM, pH 7.0) and briefly dried under a stream of N2. Hydrophobic carbon papers (Toray Carbon Paper 120, Wet-proofed, Fuel Cell Store) were punched in 14 mm-diameter disks. The punched hydrophobic carbon papers were heated in a muffle furnace with a temperature ramp rate of 5 °C/min from ambient temperature to 600°C, and dwelled for 1 hour to make the carbon paper hydrophilic. The modification of carbon paper was carried out according to the procedures showing above.

Quantitation of Surface-Attached ssDNA using Hexaammineruthenium (III) trichloride (RuHex).

The surface density of complementary ssDNA (TssDNA, molecules -cm-2) immobilized on the electrode surfaces was calculated according to the voltammetric response of a transition metal complex (RuHex) bound electrostatically with DNA-modified surfaces. After degassing with N2 for 15 mins, the ssDNA-modified electrode was immersed in a stock solution (10 mM Tris buffer, pH 7.4, containing 10 pM ReHex) for 20 mins. Two cyclic voltammogram cycles were run on the electrode from -500 to -100 mV vs. AgCl/Ag, at 50, 100 and 200 mV-s'¹ respectively. The surface density of ssDNA was then calculated from: TssDNA = Q z NA I (n F A m) where n is the number of electrons in reaction, A is the area of the working electrode, z is the charge of the RuHex, NA is Avogadro’s number, Q is the charge obtained by integration of cathodic peak in the cyclic voltammograms, and m is the number of nucleotides in the ssDNA.

Catalyst Immobilization by DNA Hybridization.

The catalyst-modified single-stranded DNA was hybridized to its complement immobilized the electrode. Generally, a solution of 20-100 pM catalyst-ssDNA conjugate (5 mM phosphate, 50 mM NaCl buffer, pH 7.0) was degassed and blanketed with N2, heated to 65 °C for 15 mins, then drop-cast (20 pL for SPE electrode, 5 pL for glassy carbon electrode) on the electrode modified with complementary ssDNA (previously covered in the same buffer without ssDNA and preheated in an oven at 65 °C for 15 mins.) This solution was then cooled slowly to ambient temperature (2-3 h) in a humidity box. The modified electrode was then washed with water and briefly dried under a stream of N2.

CO2 Reduction Product Measurements. Catalyst-modified electrodes were tested in a two-compartment low-volume electrochemical cell (Adams & Chittenden Scientific Glass Coop, USA) or customized two-compartment cell in which CO2 flowed over the electrode and exited through the working compartment. For low-volume electrochemical cell, Pt wire was used as the counter electrode, AgCl/Ag as the reference, and P5 frits (1-1.6 pm) as the separator. The customized two-compartment cell was made of polyetheretherketone (PEEK), and the working and counter electrode compartments were separated by SelemionTM membrane. The counter and reference electrodes were platinum foil (99.9% metals basis, Alfa Aesar) and Ag/AgCl leak- free reference (LF-2, Innovative Instrument Inc.), respectively. CO2 reduction products were analyzed every 5 mins via an in-line GC (SRI instruments, USA), during which the GC-sampled headspace composition was expected to reflect steady- state conditions.

GC peak areas were converted to parts-per-million (ppm) by fitting the calibration curve according to established procedures. Once these values were known, they could be converted to partial current by:

Partial current (mA) = ppm * [moles product/total moles /1000000 ppm] * [1 total mol 122.4 std. L] *[1 std. L 1 1000 see] * [(flowrate)sccm] *[1 minute 160 sec] * [n moZe D / 1 mole product] * [96485.3 C / 1 mol e-] * [1 A 1 1 C/s] * [1000 mA / 1 A]

For electrochemical reduction of CO2 to CO carried out in this paper, n = 2 and flowrate = 10 seem.

EXAMPLE 3

The following Example describes the activity of catalysts with and without being tethered to an electrode.

The activity of molecular catalysts towards electrocatalytic CO2 reduction was investigated, the results of which are shown in Table 1. A solution containing free catalyst was drop cast onto the surface of a cathode, whereafter the cathode was used for the electrocatalytic reduction of CO2 (Free Catalyst). This was compared to the activity of the molecular catalyst when tethered to an electrode (DNA-catalyst). Finally, the activity of the molecular catalyst are compared to conventional catalysts used to in conventional systems (Industry Standard).

Table 1. Electrocatalytic performance of various catalysts towards CO2 reduction.

The results in Table 1 show that the free catalyst and DNA-catalyst exhibit increased activity and turnover rates relative to the conventional catalysts used as industry standards.

EXAMPLE 4 The following Example describes the synthesis of copper nanoparticles.

An aqueous solution containing approximately 20 mL of deionized water, 40 mg of a copper salt, 180 mg of hexadecylamine (HD A), and 100 mg of a reducing agent was prepared and sonicated for 10 minutes. The solution was mixed for six hours at room temperature, whereafter the solution was then heated at 100° C for 8 hours while mixing to form copper nanoparticles. After allowing the solution to cool to room temperature, the nanoparticles were washed via repeated (e.g., 3 times) centrifugation and resuspension steps using water and/or chloroform. Table 2 shows the details of the solutions used and the primary shape of the copper nanoparticles that were synthesized.

Table 2. Identity of the copper salt, reducing agent, and resulting shape of their copper nanoparticles. FIG. 9A shows the reaction conditions under which the synthesis was success as a function of reducing agent identity. The reaction proceeded at lower temperatures under more basic conditions. FIG. 9B is an example SEM micrograph showing copper nanoparticles synthesized having a shape comprising a jack.

FIGS. 9C and 9D show SEM images and corresponding plots collected using XRD. FIG. 9C shows that particles synthesized that are essentially free of CuO. In contrast, FIG. 9D shows particles synthesized that contain CuO.

EXAMPLE 5

The following Example describes the use of copper nanoparticles as electrocatalysts.

SEM micrographs are shown in FIG. 10A of copper nanoparticles were made in accordance with the methods used in Example 4, with the respective copper salt and reducing agents. FIG. 10B shows chronoamperograms of electrocatalytic experiments using the triangular copper sheets formed from a CuBr2 precursor solution at different catalyst loading in the presence and absence of CO2. The precursor solution was dispersed on the working electrode using the additional parameters noted in FIG. 10B for each corresponding chronoamperograms.

FIG. IOC shows the product distribution obtained as a function of applied potential using the particles shown in FIG. 10A. The CuBr2 particles (e.g., the triangular sheets, CuBIG-lactose) showed an improved selectivity for ethylene production.

FIG. 10D shows the product distribution obtained for the nanoparticles as a function of shape.

While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and/or methods, if such features, systems, articles, materials, and/or methods are not mutually inconsistent, is included within the scope of the present invention.

The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

As used herein, “wt%” is an abbreviation of weight percentage.

Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and/or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMS What is claimed is:

1. A composition comprising: a copper nanoparticle, wherein a surface of the copper nanoparticle is essentially free of copper oxide.

2. A composition, comprising: a copper nanoparticle, wherein a shape of the copper nanoparticle comprises a triangular sheet and/or a jack.

3. A composition, comprising: a collection of copper nanoparticles, wherein at least 20% of the collection of nanoparticles define a set of nanoparticles having exposed surfaces comprising exposed lattice planes where at least 25% of the exposed lattice planes of the set are the same crystallographic lattice plane, and wherein the set of nanoparticles is not made via etching.

4. A composition as in claim 3, wherein at least 50% of the collection of nanoparticles have a triangular sheet and/or a jack shape.

5. A composition as in claim 3, wherein a shape of at least one of the set of nanoparticles is a triangular sheet and/or a jack shape.

6. The composition as in any one of the preceding claims, wherein the copper nanoparticle has less than or equal to 6 facets.

7. The composition as in any one of the preceding claims, wherein an average maximum dimension of the copper nanoparticle is greater than or equal to 1 nm and less than or equal to 1000 microns.

8. The composition as in any one of the preceding claims, wherein the copper nanoparticles, when configured in an electrochemical cell for carbon dioxide reduction, produce a product distribution of methane to ethanol of greater than or equal to 1 to 1 and less than or equal to 1,000 to 1.

9. The composition as in any one of the preceding claims, where the copper nanoparticle is proximate a surface of an electrode.

10. The composition as in claim 9, wherein the electrode comprises carbon.

11. The composition as in any one of the preceding claims, the composition is configured for performing catalysis.

12. A method, comprising: electrocatalytically reducing CO2 using the composition as in any one of the preceding claims.

13. The composition as in any one of the preceding claims, wherein the composition is configured to perform electrocatalytic CO2 reduction.

14. The composition as in claim 13, wherein a turnover frequency of CO2 consumption by the copper nanoparticle is greater than or equal to 10 s’¹.

15. The composition as in claim 13 or 14, wherein a turnover frequency of CO2 consumption by the copper nanoparticle is less than or equal to 10⁶ s’¹.

16. The composition as in any one of 13-15, wherein the composition is configured to produce a major product comprising ethylene during electrocatalytic CO2 reduction.

17. The composition as in any one of the preceding claims, wherein a shape of the copper nanoparticle comprises a triangular sheet and/or a jack.

18. The composition as in any one of the preceding claims, wherein a surface of the copper nanoparticle is essentially free of copper oxide.

19. A method for making copper nanoparticles, comprising: mixing a solution comprising: a monosaccharide or a di saccharide; a capping ligand; and a copper halide.

20. The method as in any one of the preceding claims, wherein the monosaccharide or the disaccharide comprises or is glucose, sucrose, fructose, ribose, lactose, and/or galactose.

21. The method as in any one of the preceding claims, wherein the capping ligand comprises or is an amine.

22. The method as in any one of the preceding claims, wherein the capping ligand comprises or is an octylamine, oleyl amine, and/or hexadecyl amine.

23. The method as in any one of the preceding claims, wherein the copper halide comprises or is copper(II) chloride and/or copper(II) bromide.

24. The method as in any one of the preceding claims, further comprising heating the solution.

25. The method as in any one of the preceding claims, further comprising washing the nanoparticles.

26. The method as in any one of the preceding claims, further comprising disposing the copper nanoparticles proximate an electrode.