KR102735762B1 - Electrocatalyst for HMF electrochemical reduction to BHMF production and its manufacturing method - Google Patents

Abstract

The present invention provides an electrode for producing BHMF through an electrochemical HMF reduction reaction, comprising a conductive substrate, on the upper portion of which a non-precious metal-based catalyst layer is formed through a hydrogen-assisted electrodeposition synthesis method, and wherein the catalyst layer has a porous structure composed of nanoparticles.
The present invention not only reduces the electrode manufacturing cost by using low-priced metals, but also maintains high efficiency, thereby reducing the process operation cost of the BHMF synthesis process through the HMF reduction reaction. By shortening the electrode manufacturing time, the cost due to the increase in the manufacturing process time can be reduced, and wastewater treatment costs can also be reduced by not using organic solvents.

Description

{Electrocatalyst for HMF electrochemical reduction to BHMF production and its manufacturing method}

The present invention relates to the manufacture of a catalyst electrode for producing BHMF through an electrochemical HMF reduction reaction and a method for manufacturing the same, and more particularly, to a method for manufacturing an electrode that suppresses hydrogen production reaction and by-product production and increases the production efficiency and selectivity of BHMF by using a non-precious metal-based catalyst electrode.

Research on using more environmentally friendly biomass energy to replace fossil fuels is increasing. Among them, biomass-based nitrification has high utility because it can synthesize high value-added carbon compounds by utilizing biomass materials. HMF is a substance obtained from lignocellulosic biomass, and is known as a dynamic platform chemical substance that can be converted into various chemical substances through redox reactions because the hydroxyl group (-OH) and carbonyl group (-C=O) are connected to the furan ring. In particular, BHMF, which can be synthesized using the two-electron reduction reaction of HMF, is an important building block chemical substance that can be used in the manufacturing industries of resins, polymers, artificial fibers, and medical products. Previous studies on BHMF production through HMF reduction reaction were mainly conducted using thermal catalysts. This reaction requires high temperature and high pressure conditions, and organic solvents or hydrogen gas are used as reducing agents (proton sources). On the other hand, electrochemical catalytic reactions can be carried out at room temperature and pressure, and water and hydrogen can be used as reducing agents instead of hydrogen and organic solvents, so the cost of process operation can be reduced, and on-site safety can be secured and waste generated during the process can be easily disposed of. Research on BHMF production through electrochemical HMF reduction reaction has been mainly conducted using silver catalysts or silver-based electrodes (Ag/Cu, Ag/carbon paper). In addition, there have been research cases that attempted synthesis using electrodes utilizing other elements. Catalysts utilizing inexpensive elements such as Bi and Sn are known to have low selectivity and relatively high overpotential, so not much research has been conducted. Existing studies have a disadvantage in that the selectivity of BHMF production decreases as the initial HMF concentration increases, making it impossible to produce BHMF efficiently at high currents. In addition, when manufacturing Bi-based electrodes, the precursor is generally manufactured by dissolving Bi salts in organic solvents. However, when using this method, the dissolution time of the Bi salts becomes long, increasing the time of the overall manufacturing process, and there is a disadvantage in that wastewater treatment of the organic solvent after use is difficult.

Republic of Korea Publication Patent No. 10-2017-0088895

In order to solve the above problems, the present invention aims to provide an electrode for producing BHMF through an electrochemical HMF reduction reaction.

In addition, the purpose is to provide a method for manufacturing an electrode for producing BHMF through the above electrochemical HMF reduction reaction.

In order to achieve the above object, the present invention provides an electrode for producing BHMF, comprising: a conductive substrate; and an electrocatalyst deposited on the conductive substrate;

The conductive substrate is characterized by being at least one selected from the group consisting of a metal foil, a metal mesh, a metal foam, and a porous carbon layer.

An electrode for producing BHMF is provided, characterized in that the above electrocatalyst has a porous dendrite structure.

In order to achieve the above other objects, the present invention comprises a first step of pretreating a conductive substrate using a 0.1 to 1M acidic solvent, acetone and ethanol;

A second step of preparing a precursor for electrochemical deposition by dissolving 0.01 to 3 M metal salt in a 0.1 to 9 M acid solution; and

A method for producing a catalyst electrode for producing BHMF from HMF through an electrochemical reduction reaction is provided, including a third step of immersing the conductive substrate in the precursor for electrochemical deposition and then applying a current of 0.01 A cm ^-2 to 10 A cm ^-2 on the substrate through an electrochemical deposition method to deposit electrocatalyst particles.

The present invention not only reduces the electrode manufacturing cost by using a low-cost non-precious metal catalyst electrode, but also maintains high efficiency and high selectivity, thereby reducing the process operation cost of the BHMF synthesis process through the HMF reduction reaction. By shortening the electrode manufacturing time, the cost due to the increase in the manufacturing process time can be reduced, and wastewater treatment costs can also be reduced by not using an organic solvent.

FIG. 1 illustrates an image of a two-electrode system used in manufacturing an electrocatalyst using an electrodeposition method according to one embodiment of the present invention.
FIG. 2 illustrates an image of a three-electrode system used when testing the performance of an electrode according to one embodiment of the present invention.
FIG. 3 is a graph showing the BHMF Faraday efficiency according to the potential of Bi, Sn, and BiSn electrodes according to one embodiment of the present invention.
FIG. 4 is a graph showing the current (J) and the faradaic efficiency (%) of BHMF when a constant voltage of -1.2 V vs. SCE (-0.5 V vs. RHE) is applied to a 0.5 M phosphate buffer having a pH of 7.2 and containing 20 mM HMF according to one embodiment of the present invention.
FIG. 5 is a graph showing the current (J) and the faradaic efficiency (%) of BHMF when a constant voltage of -2.5 V vs. SCE (-1.8 V vs. RHE) is applied to a 0.5 M phosphate buffer containing 2 M HMF according to one embodiment of the present invention.
FIG. 6 is a SEM image of a planar Bi electrode manufactured by applying a constant current of 30 mA cm ^-2 for 5 min according to one embodiment of the present invention.
FIG. 7 shows SEM images of the surfaces of porous Bi, Sn, and BiSn electrodes manufactured by applying a constant current of 5 A cm ^-2 for 10 sec according to one embodiment of the present invention.
FIG. 8 is an EDS and elemental mapping graph of a porous BiSn electrode according to one embodiment of the present invention.
FIG. 9 is an XRD analysis graph of porous Bi, Sn, and BiSn electrodes according to one embodiment of the present invention.

The present invention is described in more detail below.

According to one aspect of the present invention, an electrode for producing BHMF through a HMF reduction reaction, comprising: a conductive substrate; and a porous electrocatalyst; wherein the conductive substrate is characterized in that it is one selected from the group consisting of a metal foil, a metal mesh, a metal foam, a porous carbon foil, a porous carbon mesh, and a porous carbon foam, and the porous electrocatalyst is characterized in that it has a dendrite structure.

The above electrocatalyst can be synthesized in a short time (<1 min) through a dynamic hydrogen bubble templating (DHBT) synthesis method. The dendrite particle diameter of the electrocatalyst is preferably 10 nm to 1000 nm, and the dendrite pore size is preferably 5 μm to 400 μm. If it is out of the described range, it may be difficult to produce BHMF through the HMF reduction reaction due to the dendrite diameter. Through this structure (porous dendrite), the electron and mass transfer efficiency of the electrocatalyst can be improved.

The porous catalyst is preferably one or more than one selected from the group consisting of bismuth (Bi), tin (Sn), lead (Pb), titanium (Ti), mercury (Hg), gold (Au), platinum (Pt), iridium (Ir), indium (In), cadmium (Cd), silver (Ag), palladium (Pd), rhodium (Rh), gallium (Ga), zinc (Zn), copper Cu, nickel (Ni), cobalt (Co), iron (Fe), aluminum (Al), and cerium (Ce). More preferably, it may be bismuth (Bi), tin (Sn), indium (In), cerium (Ce), zinc (Zn).

The electrode of the present invention can selectively suppress hydrogen production reaction, which is a competitive reaction when reducing HMF electrochemically, and can maintain the faradaic efficiency of BHMF at 90% or higher even under current conditions of 100 mA cm ^-2 or higher. Therefore, it is preferable that the faradaic efficiency of the electrode is 90 to 100%.

Preferably, the present invention manufactures an electrode under the same electrodeposition conditions by changing the molar ratio of dissolved Bi ³⁺ : Sn ²⁺ among the electrodeposition catalysts. All three types of catalysts were used, and the catalyst manufactured at a ratio of 0:10 or 10:0 is a single metal catalyst (Bi or Sn), and the catalyst manufactured at a ratio of 7:3 to 3:7 is a bimetallic catalyst mixed with two elements, Bi and Sn. When BiSn (5:5), which has the best performance among these, and the single metal electrode Bi and Sn were selected and their BHMF production performances were compared, excellent productivity performance was observed.

The chemical reaction by which HMF of the present invention is reduced to BHMF is as follows.

Electrodes composed of Bi, Sn, or bimetallic BiSn can suppress the hydrogen evolution reaction (HER), which is a competitive reaction of HMF reduction reaction, and show selectivities of 100%, 70%, and 88% for BHMF production, respectively. When the pH of the electrolyte is neutral (6–8), the BHMF faradaic efficiency of the BiSn electrode is over 90% and close to 100%, which confirms that this is the most suitable pH for the BHMF production reaction (see Table 4). In addition, the BiSn porous bimetallic electrode can stably operate for 30 h in a phosphate buffer at neutral pH containing 20 mM HMF with a BHMF selectivity of over 95%, and the voltage V of -2.5 V vs. When SCE is applied, it can operate stably for 8 hours at a current density of -100 to -200 mA cm ^-2 and a selectivity of nearly 100% for BHMF (see Fig. 5). In addition, the electrode manufacturing time can be shortened, which reduces the cost due to the increased manufacturing process time, and wastewater treatment costs can also be reduced because no organic solvent is used.

According to another aspect of the present invention, a method for producing a catalyst electrode for producing BHMF from HMF through an electrochemical reduction reaction is provided, comprising: a first step of pretreating a conductive substrate using a 0.1 to 1 M acidic solvent, acetone and ethanol; a second step of preparing a precursor for electrochemical deposition by dissolving a 0.01 to 3 M metal salt in a 0.1 to 9 M acidic solvent; and a third step of immersing the conductive substrate in the precursor for electrochemical deposition and then applying a current of 0.01 A cm ^-2 to 10 A cm ^-2 onto the substrate through an electrochemical deposition method to deposit electrocatalyst particles.

In the first step, the acidic solvent is preferably a 0.1 to 1 M nitric acid or hydrochloric acid solution. In the second step, it is preferable to prepare a precursor for electrochemical deposition by dissolving a metal salt when preparing a precursor. It is preferable that the metal salt is dissolved in an acidic solvent so that the salt exists as an ion and thus exists as a metal ion.

In the second step, if the concentration of the acid solvent is lower than 0.1 M, it is a low concentration for dissolving the metal salt, and if the acid concentration is higher than 9 M, the acid concentration is too high and is not suitable for preparing a precursor for deposition. More preferably, it is 0.1 to 5 M. If the concentration of the metal salt is lower than 0.01 M, the electrodeposition time increases due to the low concentration and coating is difficult, and if it is higher than 3 M, the metal salt suppresses the hydrogen reaction, making it difficult to grow into a porous structure. More preferably, it is 0.01 to 2 M, and most preferably, it can be 0.01 to 1 M.

The acidic solvent may be one or more selected from H ₂ SO ₄ , HCl, HClO ₄ , HNO ₃ , H ₃ PO ₄ , CH ₃ COOH, and HCOOH. The concentration of the acidic solvent is preferably 0.1 to 1 M. If the concentration of the acidic solvent is less than 0.1 M, the acid utility is too low for pretreating a conductive substrate as an acid, and if it is more than 1 M, the acid concentration is high and is not suitable for pretreating a conductive substrate.

The concentration of the metal ion is preferably 0.005 M to 0.5 M, and more preferably 0.01 M to 0.5 M. The applied current is preferably 0.05 A cm ^-2 to 10 A cm ^-2 , and more preferably 0.1 A cm ^-2 to 10 A cm ^-2 . The applied voltage may vary depending on the selection of the anode. If it is less than the above range, electrode formation may be difficult, and if it exceeds the range, formation of the dendrite structure of the porous electrocatalyst may be difficult.

In the present invention, hydrochloric acid, acetone, and ethanol are used as substitutes for organic solvents widely used in the manufacture of conventional Bi-based electrodes, so that wastewater treatment facilities are not required, and it is economical and can solve environmental pollution problems. After dissolving Bi ³⁺ and Sn ²⁺ ions in a ratio of 3:7 to 7:3, a porous dendritic BiSn bimetallic catalyst is coated on a copper substrate by applying a constant current for less than 1 minute using an electrode composed of a copper substrate and a platinum substrate. The manufactured electrode is washed and then dried. When manufacturing Bi, Sn single element electrodes, the above-mentioned manufacturing process is performed only by changing the electrodeposition precursor to which only Bi ³⁺ or Sn ²⁺ ions are added.

In order to confirm the effect due to the structure, a planar-shaped Bi or Sn electrode was synthesized by applying a constant current of 10 to 60 mA cm ^-2 from the same precursor and compared with the porous dendritic electrode, it was confirmed that the electrode produced with the porous structure generally showed higher current density and Faraday efficiency of BHMF production at the same voltage. Therefore, it can be seen that the porous dendritic structure has a great effect on the catalytic activity (see Table 8 and Fig. 6).

To evaluate the HMF reduction performance of the fabricated electrode, an electrochemical reduction experiment was performed with a three-electrode system in a 0.5 M borate buffer (pH 9.2) solution containing 20 mM HMF. The fabricated electrode serves as the working electrode, a saturated calomel electrode (SCE) serves as the reference electrode, and the counter electrode may be one selected from the group consisting of stainless steel, graphite, platinum, nickel, and Ni(OH) ₂ , preferably platinum or Ni(OH) ₂ . In addition, a membrane (PEM) film is formed between the working electrode and the reference electrode & counter electrode.

In this specification, when a part is said to "include" a certain component, this does not mean that other components are excluded, unless otherwise specifically stated, but that other components may be included. In addition, the terminology used in this specification is for the purpose of describing embodiments, and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated in the phrase.

In this document, the expressions "A or B," "at least one of A and/or B," or "one or more of A or/and B" can include all possible combinations of the listed items. For example, "A or B," "at least one of A and B," or "at least one of A or B" can all refer to (1) including at least one A, (2) including at least one B, or (3) including both at least one A and at least one B.

Hereinafter, the present invention will be described in more detail by way of preferred embodiments. However, it will be apparent to those skilled in the art that these embodiments are intended to explain the present invention more specifically and that the scope of the present invention is not limited thereby.

<Example>

Example 1 - Fabrication of an electrode system

The copper substrate was immersed in a 0.5 M nitric acid solution for 5 minutes to remove the surface oxide film. Then, it was immersed in acetone and ethanol solutions for 5 minutes each to remove surface organic contaminants, and then washed with DI water. Then, it was dried using an air gun. Bi( _NO3 ) _35H2O and SnCl2 _{· 2H2O} were added in different ratios to a 1.5 M sulfuric acid solution and sonicated for 1 minute. The ratios of Bi and Sn were 10:0, ₇ :3, 5:5, 3:7, and 0:10, and the total concentration of Bi ions and Sn ions was 0.1 M. Cu foil was immersed in a 0.5 M hydrochloric acid solution, sonicated for 2 minutes, and dried using an air gun. A constant current of 30 mA cm ^-2 was applied for 30 s by connecting it to a power supply together with a Pt foil, and then a constant current of 5 A cm ^-2 was applied for 10 s. At this time, the cathode was Cu foil and the anode was Pt foil (see Fig. 1). The fabricated electrode was washed with di-water and then dried at room temperature.

Example 2 - Electrode Performance Analysis

(1) BHMF generation

The experimental device was configured with a three-electrode system and an electrolysis experiment was performed in a pH 9.2, 0.5 M borate buffer containing 20 mM HMF. During the electrolysis experiment, a certain amount of sample was extracted from the electrolyte over time, diluted to 1/10, and the amount of product BHMF was measured using HPLC and the faradaic efficiency was calculated. When calculating the efficiency, since 2 electrons are required to generate BHMF, it is calculated by multiplying by 2:

Q is the amount of charge (C) flowing during the electrochemical reaction, F is the Faraday constant (96485 C/mol), and n is the number of moles of BHMF produced (mol).

(2) Measurement of charge transfer resistance of electrodes

The resistance during the electrochemical reaction was measured using electrochemical impedance spectroscopy (EIS). In the electrolyte above, the values were measured and calculated at 10 mV intervals from 0.01 to 100,000 Hz (-1.0 V vs. SCE), and the smaller the charge transfer resistance value, the better the reaction. The circuit model below was used for the analysis.

Example 3 - SEM Analysis

SEM (Scanning Electron Microscope) analysis was performed using FE-SEM, Hitachi S4800, and images of the electrode surface were taken by applying an accelerating voltage of 5.0 kV.

Example 4 - Evaluation of durability of electrodes

The current (J) and faradaic efficiency (%) were measured when a voltage of -1.2 V vs. SCE was applied to 0.5 M phosphate buffer (pH 7.2) containing 20 mM HMF, and the current (J) and faradaic efficiency (%) were measured when a voltage of -2.5 V vs. SCE was applied to 0.5 M phosphate buffer (pH 7.2) containing 2 M HMF.

Example 5 - EDS and elemental mapping analysis

EDS and elemental mapping were performed using OXFORD's Ultim Extreme, Model: SU8220 equipment attached to a SEM.

Example 6 - XRD Analysis

Observations were made using the EMPYREAN equipment from Panalytical using Cu-Kα radiation (40 kV, 30 mA) at a wavelength of 1.5406 Å.

<Results and Evaluation>

Comparison of Onset Potential and Current Size According to Bi:Sn Molar Ratio

Molar ratio Including HMF HMF not included Bi:Sn
Onset potential j @ -1.4 V vs. SCE Onset potential 0 : 10
(porous Sn) -1.22 V vs. SCE -3.4 mA cm ^-2 -1.27 V vs. SCE 3 : 7
-1.18 V vs. SCE -3.6 mA cm ^-2 -1.28 V vs. SCE 5 : 5
(porous Bi/Sn) -1.07 V vs. SCE -5.4 mA cm ^-2 -1.23 V vs. SCE 7 : 3
-1.09 V vs. SCE -4.8 mA cm ^-2 -1.23 V vs. SCE 10 : 0
(porous Bi) -1.10 V vs. SCE -4.1 mA cm ^-2 -1.23 V vs. SCE

Table 1 shows a comparison of the onset potential and current magnitude according to the molar ratio of Bi and Sn in the electrodeposition precursors. The onset potential and current magnitude were compared through cyclic voltammetry (CV) in a borate buffer (pH 9.2) containing 20 mM HMF (not included). Referring to Table 1, the Bi and Sn ratio with the highest HMF conversion efficiency was 5:5, which showed the highest current and the lowest onset potential at the same potential (-1.4 V vs. SCE). When HMF was not included, the onset potential did not show a significant difference.

Electrochemical properties

electrode Rt(Ohm cm ^-2 ) porous Sn 2001 porous Bi 308 porous Bi/Sn 255

Table 2 shows the charge transfer resistance ( R _ct ) comparison of three electrodes through EIS. At this time, 0.5 M borate buffer (pH 9.2) and 20 mM HMF were included as electrolytes. Referring to Table 2, the charge transfer resistance of porous Bi/Sn was the lowest. A lower charge transfer resistance means that charge transfer proceeds more smoothly. Therefore, it was found that the most charge transfer occurred in porous BiSn when the same voltage was applied.

Electrochemical performance

Table 3 shows a comparison of catalytic performance through the amount of BHMF generated according to the applied potential. The values for current, BHMF generation per hour, BHFM Faradaic efficiency, and partial current density (current density × Faradaic efficiency) according to the applied potential for porous Sn, Bi, and BiSn are shown. The BHMF generation rate of porous BiSn was the highest among the three types of electrodes, but the BHMF Faradaic efficiency was lower at low potentials and higher at high potentials (>-1.4 V vs. SCE) than that of porous Bi. The highest Faradaic efficiencies for BHMF generation of Sn, Bi, and BiSn electrodes were 70%, 97%, and 88%, respectively.

FIG. 3 is a graph showing the BHMF Faraday efficiency according to the potential of the Bi, Sn, and BiSn electrodes according to an embodiment of the present invention. Referring to FIG. 3, the efficiency of porous BiSn is higher than that of porous Sn, but the efficiency of porous Bi is higher in the voltage range of -1.3 to -1.0 V vs. SCE. FIG. 3 is a graph showing the Faraday values of Table 3, and the Faraday efficiency of the porous Bi electrode was the highest when E<-1.3 V vs. SCE, and the Faraday efficiency of the porous BiSn electrode was the highest when E>-1.4 V vs. SCE.

Potential-dependent BHMF faradaic efficiency as a function of pH using porous BiSn electrode

Table 4 shows the BHMF faradaic efficiency (%) at different potentials according to pH of the porous Bi/Sn electrode. In order to compare the electrode performance according to the electrolyte pH, the potential unit was unified as RHE using the following mathematical equation 2.

Referring to Table 4, the highest BHMF faradaic efficiency of 99.78% was achieved in a pH 7.2 phosphate solution. This means that the BHMF production reaction proceeds most smoothly in a neutral solution. The pH solutions used were acid buffer (KCl, HCl) at pH 2, phosphate buffer at pH 5.8 and 7.2, borate buffer at pH 9.2, and KOH solution at pH 13.5.

Evaluation of porous BiSn electrode performance according to HMF concentration

Tables 5, 6, and 7 show the current at different potentials and the BHMF Faraday efficiency of the porous BiSn electrode at HMF concentrations of 20 mM, 200 mM, and 2000 mM, respectively. Referring to Tables 5, 6, and 7, it can be seen that the potential range where the Faraday efficiency of BHMF is over 90% improved as the HMF concentration increased. Therefore, BHMF could be efficiently produced under high current conditions by increasing the HMF concentration. In previous studies, it was reported that the BHMF production efficiency decreased as the HMF concentration increased, and therefore, HMF could be selectively converted to BHMF only under current conditions of around 10 mA cm ^-2 . On the other hand, in the present study, BHMF could be produced with high efficiency and high current (10–150 mA cm ^-2 ) regardless of the HMF concentration.

Electrode durability test

FIG. 4 is a graph showing the current (J) and the faradaic efficiency (%) when a voltage of -1.2 V vs. SCE is applied to 0.5 M phosphate buffer containing 20 mM HMF according to an embodiment of the present invention, and FIG. 5 is a graph showing the current (J) and the faradaic efficiency (%) when a voltage of -2.5 V vs. SCE is applied to 0.5 M phosphate buffer containing 2 M HMF according to an embodiment of the present invention.

Referring to Fig. 5, the current or the faradaic efficiency of BHMF decreased because the HMF concentration continuously decreased over time. However, when the electrolyte was changed to the same as the initial one, the initial performance was restored. Through this, it was possible to prove that the performance degradation was due to the electrolyte, not the electrode.

Confirming the dendrite structure

FIG. 6 is a SEM image of a planar Bi electrode manufactured by applying a constant current of 30 mA cm ^-2 for 5 min according to one embodiment of the present invention.

Referring to Fig. 6, in order to confirm the effect due to the structure, a planar-shaped Bi or Sn electrode was synthesized by applying a constant current of 30 mA cm ^-2 for 5 min from the same precursor, and the result was compared with a porous dendritic electrode. According to Table 8, it was confirmed that the electrode generated with a porous structure generally showed higher current density and Faraday efficiency of BHMF generation at the same voltage. Therefore, it could be seen that the porous dendritic structure had a great influence on the catalytic activity.

E(V vs. SCE) Porous Bi
J(mA cm ^-2 ) Planar Bi
J(mA cm ^-2 ) Porous Bi
FE _BHMF (%) Planar Bi
FE _BHMF (%) E(V vs. SCE) Porous Bi
J(mA cm ^-2 ) Planar Bi
J(mA cm ^-2 ) Porous Bi
FE _BHMF (%) Planar Bi
FE _BHMF (%) -1.1 -0.55 24.39 -1.1 -0.67 8.27 -1.2 -1.83 -0.35 97.68 21.52 -1.2 -0.85 -0.45 23.03 4.83 -1.3 -4.14 -1.14 97.13 66.95 -1.3 -2.69 -0.96 55.21 39.33 -1.4 -6.64 -3.38 81.40 92.81 -1.4 -5.30 -4.46 68.49 65.08 -1.5 -8.74 -4.10 62.77 86.53 -1.5 -6.67 -6.37 69.40 64.47 -1.6 -10.95 -4.57 53.88 67.68 -1.6 -6.86 -5.95 63.53 62.84

SEM Analysis

Fig. 7 illustrates SEM images of the surfaces of Bi, Sn, and BiSn electrodes according to one embodiment of the present invention. Referring to Fig. 7, although the micro-sized electrodes exhibit a porous structure, when enlarged to the nano-sized electrodes, it was confirmed that each electrode formed a dendrite structure.

Referring to Fig. 8, the EDS results confirmed that the actual loaded atomic ratio (Bi:Sn) in the BiSn electrode deposited from a solution with a Bi ³⁺ : Sn ²⁺ molar ratio of 5:5 was 3:1. In addition, referring to the elemental mapping results, it was confirmed that Bi was evenly coated and Sn was generally concentrated on the surface.

Referring to Figure 9, the Bi, Sn, and BiSn electrodes are composed of a polycrystalline zero-valent metal form. In addition, it was confirmed that BiSn is a mixture of Bi and Sn.

Hydrogen suppression reaction results

Electrodes composed of Bi, Sn or bimetallic BiSn can suppress the hydrogen evolution reaction (HER), which is a competitive reaction of HMF reduction reaction, and show selectivity of 100%, 70% and 88% for BHMF production, respectively. When the pH of the electrolyte is 7.2, the BHMF faradaic efficiency of the BiSn electrode is 99.78%, which confirms that this is the most suitable pH for the BHMF production reaction (see Table 4).
In addition, the BiSn porous bimetallic electrode can stably operate for 30 h in a phosphate buffer (pH 7.2) containing 20 mM HMF with a BHMF selectivity of more than 95%, and can stably operate for 8 h at a BHMF selectivity of nearly 100% while maintaining a current density of -140 mA cm ^-2 when -2.5 V vs. SCE is applied in phosphate buffer (pH 7.2) containing 2 M HMF (see Fig. 5). In addition, the manufacturing time of the electrode was shortened, which reduced the cost due to the increased manufacturing process time, and the cost of wastewater treatment was also reduced because no organic solvent was used.

In Table 1, it was confirmed that the onset potential in the solution without HMF was higher than that in the solution containing HMF. This means that the HMF reduction reaction proceeds more smoothly than the hydrogen production reaction in the HMF-containing electrolyte. Referring to Table 9 below, it was found that the faradaic efficiency of hydrogen generated at the porous Bi electrode was less than 1% when a 0.5 M borate buffer solution containing 20 mM HMF was used as the electrolyte (-1.2 to -1.4 V vs. SCE).

E(V vs. SCE) Porous Bi
J(mA cm ^-2 ) Planar Bi
J(mA cm ^-2 ) -1.1 24.39 -1.2 97.68 0.36 -1.3 97.13 0.27 -1.4 81.40 0.92 -1.5 62.77 3.22 -1.6 53.88 7.91

The foregoing has broadly described the features and technical advantages of the present invention so that the scope of the claims to be described later may be better understood. Those skilled in the art will appreciate that the present invention may be implemented in other specific forms without changing the technical idea or essential features thereof. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the claims and their equivalents should be interpreted as being included in the scope of the present invention.

Claims (5)

An electrode for producing BHMF, comprising: a conductive substrate; and an electrocatalyst deposited on the conductive substrate;
The above conductive substrate is at least one selected from the group consisting of a metal foil, a metal mesh, a metal foam, and a porous carbon layer,
The above electrocatalyst is a bismuth (Bi) monometal or a bimetal (BiSn) composed of bismuth (Bi) and tin (Sn),
Among the precursors for electrochemical deposition for synthesizing the above electrocatalyst, the molar ratio of bismuth (Bi) and tin (Sn) is 10:0 to 5:5.
An electrode for producing BHMF, characterized in that the electrocatalyst has a porous dendrite structure.
In paragraph 1,
An electrode for producing BHMF, characterized in that the dendrite particle diameter of the above electrocatalyst is 10 nm to 1000 nm.
In paragraph 1,
An electrode for producing BHMF, characterized in that the BHMF faradaic efficiency of the electrode is 90 to 100%.
A first step of pretreating a conductive substrate using 0.1 to 1 M acidic solvent, acetone and ethanol;
A second step of preparing a precursor for electrochemical deposition by dissolving a metal salt of 0.01 to 3 M, wherein the metal is bismuth (Bi) and tin (Sn), and the molar ratio of bismuth (Bi) and tin (Sn) is 10:0 to 5:5 in a 0.1 to 9 M acid solution; and
A method for producing a catalyst electrode for producing BHMF from HMF through an electrochemical reduction reaction, comprising: a third step of immersing the conductive substrate in the precursor for electrochemical deposition, and then applying a current of 0.01 A cm ^-2 to 10 A cm ^-2 to the upper portion of the substrate through an electrochemical deposition method to deposit bismuth (Bi) monometal or a bimetal (BiSn) composed of bismuth (Bi) and tin (Sn) on the surface of the conductive substrate. delete