CN115770621A - Preparation method and application of bimetallic MOF (metal organic framework) anchored Pt nanocluster catalyst - Google Patents

Abstract

The invention discloses a preparation method and application of a bimetallic MOF anchored Pt nanocluster catalyst, wherein the catalyst is Pt _NC NiMn-MOF nano material, the catalyst is Pt _NC NiMn-MOF nanomaterial, which in an X-ray diffraction spectrum of the nanomaterial has a monoclinic nickel-based metal organic framework (Ni-MOF) structure, wherein the corresponding XRD diffraction angles 2 theta range from 5 degrees to 50 degrees, and obvious XRD diffraction peaks with 2 theta angles of 8.9 degrees, 15.5 degrees, 28.3 degrees and 30.6 degrees and the like respectively correspond to (200), (400), (20-2) and (311) crystal faces, pt and Pt in the NiMn-MOF structure _NC The NiMn-MOF composite nano material not only can produce hydrogen by fully decomposing urea for industrial application, but also can meet the requirements of urea wastewater treatment in various occasions such as industry, life and the like, and realizes the reclamation of wastewater and the maximization of energy utilization.

Description

Preparation method and application of bimetallic MOF-anchored Pt nanocluster catalyst

technical field

The invention relates to the technical field of nanometer electrocatalytic materials, in particular to a preparation method and application of a bimetallic MOF-anchored Pt nanocluster catalyst.

Background technique

The increasing energy crisis and environmental pollution force us to explore sustainable alternative energy sources. Hydrogen energy has the advantages of high combustion calorific value, high energy density, and non-polluting products, and has become one of the clean energy sources with the most development potential. Green and sustainable electrochemical water splitting for hydrogen production is an ideal route to mass-produce high-purity _H2 , and the corresponding electrocatalytic hydrogen evolution reaction (HER) has attracted extensive attention. Generally speaking, the efficiency of electrochemical water splitting for hydrogen production depends on the catalytic activity and stability of HER catalysts. Efficient HER electrocatalysts need to accelerate the slow reaction kinetics and reduce the electrode overpotential. Currently, commercial Pt/C is still the main catalyst for hydrogen production. However, the low abundance and high cost of platinum undoubtedly hinder its large-scale application. Therefore, it is increasingly urgent to develop efficient, stable and cheaper hydrogen-producing electrocatalysts.

Meanwhile, the complex four-electron process of anodic oxygen evolution reaction (OER) in electrochemical water splitting leads to its large driving voltage (typically ≥1.8 V), low energy efficiency, and high cost of hydrogen production. Therefore, replacing OER with other anodic oxidation reactions with lower thermodynamic voltages will enable energy-efficient hydrogen production. Among many anodic oxidation reactions, the urea oxidation reaction (UOR, CO(NH ₂ ) ₂ +6OH ^- →N ₂ +CO ₂ +5H ₂ O+6e ^- ) is due to its inherently low thermodynamic equilibrium potential (0.37 V, relative to Because of the reversible hydrogen electrode (RHE)), the overall potential of the UOR is significantly lower than that of the OER, thus arousing extensive research interest. Coupling UOR with HER (HER(−)‖UOR(+)) for overall urea electrolysis can not only produce hydrogen with low energy consumption, but also purify urea-rich wastewater, thus showing great potential for practical application.

In addition, most non-precious metal-based electrocatalysts exist in the form of powder, so binders are required to load them on working electrodes such as glassy carbon and bisulfite plates, and the fabrication process is cumbersome. In addition, most binder materials such as Nafion and poly Vinylidene fluoride is expensive, which limits its large-scale application to a large extent. The use of a binder will not only reduce the number of exposed active sites of the catalyst, but also reduce the overall conductivity of the product electrode. Combined with the degree of binder and electrocatalyst compounding, they cannot resist the stress generated during high current density operation of large catalysts, resulting in greatly reduced catalyst stability. An effective strategy to solve the above problems is the in situ growth-conducting three-dimensional porous framework composite nanocatalysts.

Metal-organic frameworks (MOFs) composed of metal nodes and organic ligands, as an emerging three-dimensional porous composite nanostructure, are considered as a class of catalytic electrode materials with great application prospects. On the one hand, MOFs have abundant and uniformly dispersed catalytic metal nodes, which endow them with a large number of active sites. On the other hand, MOF, as a porous solid material, can be used for both heterogeneous and homogeneous catalysis and can be recycled and reused after the catalytic reaction is completed. However, for most MOF materials, poor intrinsic properties, relatively low electrical conductivity, and poor stability are key issues. In situ growth of electrocatalysts onto the surface of NF frameworks can ensure intimate contact between electrocatalysts and substrates for charge transport at the electrocatalyst/substrate interface, and the mechanical stability of corresponding catalytic electrodes can also be greatly improved. Considering the poor conductivity and poor stability of MOFs, they are rarely directly used as electrocatalysts for HER and UOR. Instead, it is usually a carbon-based composite catalyst used as a metal after high-temperature heat treatment to become a catalytically active species. However, heat treatment may damage the advantages of the ordered porous structure of MOFs, resulting in aggregation of metal centers and loss of active centers. Based on this, catalyst loading of MOFs on porous conductive substrates, such as in situ growth of MOFs on NFs, is considered to be an effective way to overcome the aforementioned low electrical conductivity and low mass permeability.

In order to further improve the conductivity and catalytic activity of MOF-based catalytic electrode materials, it is considered an effective way to modify trace amounts of noble metals onto the surface of MOF structures, and further reduce the size of the modified noble metals to nano-clusters (Nano-clusters). ) scale is bound to greatly improve the catalytic activity and stability of the composite catalyst. This is because the nanocluster catalyst composed of several atoms has a high atom utilization rate and its own unique electronic structure and geometric configuration, which can maximize the conversion of substances during the catalytic reaction and accelerate the reaction rate. Although various noble metal nanoclusters have been continuously reported in the past few years, they play an important role in the field of electrocatalysis. However, due to the large surface energy of cluster atoms, metal atoms are prone to migration and aggregation, resulting in a decrease in their catalytic activity. Therefore, how to stabilize nanocluster metal atoms on a certain carrier is the key to preparing highly active nanoclusters. Although many synthetic methods, such as chemical vapor deposition, high-temperature pyrolysis, atomic layer deposition, and microwave heating, have been proven to stabilize nanoclusters, most of them are complex and require high temperature or high pressure conditions. Therefore, it is a technical problem to be solved urgently by those skilled in the art to develop and design a general strategy with simple preparation and low cost to realize metal-organic framework nanomaterials anchoring Pt nanoclusters.

Contents of the invention

Therefore, the main purpose of the present invention is to provide a preparation method and application of a bimetallic MOF-anchored Pt nanocluster catalyst to solve the problems in the background technology.

It should be noted that the metal-organic framework (MOF) precursor prepared by this method is a promising catalytic material, which is constructed by metal ions/clusters and organic linkers, which can provide clear structures and well-defined active centers, It is easy to adjust the electronic structure of the metal site; and the MOF precursor has a rich pore structure and a large specific surface area, which is easy to contact with the electrolyte, which is conducive to accelerating the mass transfer process and effectively reducing (HER(−)‖UOR( +) The overall energy consumption of the electrolytic cell. Loading Pt nanoclusters on the MOF carrier by room temperature wet chemical etching can not only improve the utilization rate of Pt, but also increase the electrocatalytic activity of composite nanomaterials, and this method is for industrial application materials The research provides a new synthesis idea.

In order to solve the above technical problems, the present invention provides the following technical solutions:

A bimetallic MOF-anchored Pt nanocluster catalyst, the catalyst is a Pt _NC /NiMn-MOF nanomaterial, which exhibits a monoclinic nickel-based metal-organic framework (Ni-MOF) structure in its X-ray diffraction spectrum , the corresponding XRD diffraction angle 2θ ranges from 5° to 50°, and the obvious XRD diffraction peaks appearing at 2θ angles of 8.9°, 15.5°, 28.3° and 30.6° correspond to (200) in the NiMn-MOF structure, respectively. , (400), (20-2) and (311) crystal planes.

The present invention also provides a method for preparing a bimetallic MOF-anchored Pt nanocluster catalyst, wherein the catalyst is Pt _NC /NiMn-MOF, and the method is as follows: using metallic nickel and manganese as metal nodes, and using terephthalmic Formic acid was used as an organic ligand to in situ grow NiMn-MOF precursors on nickel foam, and then use room temperature wet chemical etching to load Pt nanoclusters on the surface of NiMn-MOF precursors to obtain Pt _NC /NiMn-MOF composite nanostructures. Material.

Further, the preparation method includes the following steps:

Step (1): pretreatment of nickel foam;

Step (2): adding metal nickel salt, metal manganese salt and terephthalic acid to the solvent, the solvent

The agent is composed of ethanol, N,N-dimethylformamide and deionized water, and stirred evenly to obtain an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction. Preferably, the reaction temperature of the hydrothermal reaction is 120°C~160°C. The time is 12 h~24 h;

Step (4): Take out the reacted nickel foam, wash with alcohol, and dry at room temperature to obtain

Bimetallic organic framework NiMn-MOF precursor;

Step (5): Submerge the obtained NiMn-MOF precursor in a certain amount of chloroplatinic acid solution,

React in a warm and dark environment for 1 h, and then wash the reacted nickel foam with alcohol and dry it in vacuum to obtain Pt _NC /NiMn-MOF nanomaterials. Preferably, the concentration of chloroplatinic acid solution is 1 mg/mL~3 mg/mL mL.

Pt _NC /NiMn-MOF is a NiMn-MOF nanomaterial with regular nanosheet morphology formed by using Ni and Mn as metal sites and p-dibenzoic acid as an organic ligand. Highly active Pt _NC /NiMn-MOF composite nanomaterials prepared by wet chemical etching.

The method for preparing the nano-cluster/MOF composite structure disclosed by the invention is simple, has low energy consumption, and is suitable for industrial production. A synthetic dual-function MOF-anchored Pt nanocluster catalyst prepared by the method of the present invention can be used as a catalyst for high-current HER, UOR and urea degradation applications. It is superior to commercial Pt/C, and at the same time, the method for preparing nanoclusters is simple, which provides a new idea for the synthesis of highly active nanocluster catalysts.

The method for synthesizing bimetallic organic framework nanomaterials in the above one-step method, in step (2), the metal nickel salt is nickel nitrate [Ni(NO ₃ ) ₂ or Ni(NO ₃ ) ₂ 6H ₂ O], nickel sulfate [NiSO _4. NiSO ₄ ·H ₂ O, NiSO ₄ ·2H ₂ O, NiSO ₄ ·4H ₂ O, NiSO ₄ ·6H ₂ O or NiSO ₄ ·7H ₂ O] or nickel chloride [NiCl ₂ , NiCl ₂ ·6H ₂ O]; metal manganese salts are manganese nitrate [Mn(NO ₃ ) ₂ ∙4H ₂ O or Mn(NO ₃ ) ₂ ∙2H ₂ O], manganese sulfate [MnSO ₄ ∙7H ₂ O, MnSO ₄ ·H ₂ O or MnSO ₄ ·4H ₂ O] or manganese chloride [MnCl ₂ , MnCl ₂ ∙4H ₂ O]; the solvent consists of N,N-dimethylformamide, ethanol and deionized water.

Preferably, in step (2), the molar ratio of metal nickel salt, metal manganese salt and terephthalic acid is (0.1~1.0):(0.1~1.0):(0.1~1.0).

Preferably, in step (2), the volume ratio of the solvent N,N dimethylformamide, ethanol and deionized water is 4:3:1.

Preferably, the drying temperature in step (5) is 60 °C, and the drying time is 8 h.

The present invention also claims to protect the bimetallic MOF-anchored Pt nanocluster catalyst prepared by the above method. The nanocluster synthesis method is that the nanomaterial with a nanosheet structure formed by a metal organic framework is used as a precursor. Chloroplatinic acid at room temperature Pt _NC /NiMn-MOF composite nanomaterials were synthesized under aqueous etching; this material can be used as an electrocatalyst for high-current HER, urea electrocatalysis, and electrocatalysis of urea degradation to improve catalytic efficiency.

The technical solution of the present invention has achieved the following beneficial technical effects:

The invention provides a novel bimetallic MOF-anchored Pt nanocluster catalyst with excellent performance and wide application.

The bimetallic MOF anchored Pt nanocluster catalytic electrode nanomaterial synthesized by the present invention firstly uses Ni and Mn as metal nodes, and prepares NiMn-MOF nanomaterial precursor with terephthalic acid as organic ligand; Pt nanoclusters were loaded onto MOF precursors by chemical etching. The present invention overcomes the disadvantages of complex synthetic pathways for synthesizing nanoclusters in other existing technologies, and also overcomes the problems of instability and single function of conventional MOF powder electrodes.

The Pt _NC /NiMn-MOF composite nanomaterial nanomaterial prepared by the present invention only needs overpotentials of 56 mV, 170 mV and 289 mV in the electrocatalytic hydrogen evolution process, and can reach 100 mA·cm ^-2 and 500 mA·cm ^{-2 2} and a current density of 1000 mA·cm ^-2 provides a new idea for the preparation of industrial hydrogen production materials. At the same time, the nanomaterial can quickly and efficiently degrade urea in urea wastewater into N ₂ and CO ₂ , and the corresponding urea degradation rate (electrolyte is 1.0 mol/L KOH +0.33 mol/L Urea) in a short time It can reach 96.1%.

Description of drawings

Figure 1 is a schematic diagram of the synthesis of a bimetallic MOF-anchored Pt nanocluster catalyst in the embodiment of the present invention;

Fig. 2 is an XRD spectrum (NiMn-MOF and Pt _NC /NiMn-MOF) of a bimetallic MOF-anchored Pt nanocluster catalyst in the embodiment of the present invention;

The scanning electron micrograph of a kind of bimetallic NiMn-MOF catalyst nanomaterial prepared in the embodiment of the present invention in Fig. 3, wherein a is the SEM picture, and b is the EDS spectrum of the material component;

Fig. 4 is a scanning electron microscope image of a bimetallic MOF-anchored Pt nanocluster catalyst nanomaterial prepared in an example of the present invention, where a is the SEM image of Pt _NC /NiMn-MOF, and b is the EDS image.

Figure 5 is a scanning transmission electron microscope (TEM) picture of a bimetallic energy MOF-anchored Pt nanocluster catalyst prepared in an embodiment of the present invention, where a and b are the TEM pictures of Pt _NC /NiMn-MOF and the corresponding positions Zoom in;

Figure 6 shows the HER performance diagram of a bimetallic energy MOF-anchored Pt nanocluster catalyst prepared in the embodiment of the present invention and its comparison sample under high current conditions, where a is the LSV polarization curve, and b is the corresponding performance histogram . ;

The UOR performance figure of a kind of bimetallic MOF catalyst prepared in the embodiment of the present invention and its comparative sample in Fig. 7, wherein a is the UOR polarization curve (LSV) figure of Pt _NC /NiMn-MOF and its comparative sample, and b is Performance comparison chart of samples at different current densities.

Figure 8 HER and UOR stability test diagram of a bimetallic MOF-anchored Pt nanocluster catalyst prepared in the example of the present invention, where a is the Pt _NC /NiMn-MOF after 1000 CV cycles in the HER process LSV performance comparison chart, b is the LSV performance comparison chart of Pt _NC /NiMn-MOF after 1000 CV cycles in the UOR process;

Figure 9 is the urea degradation performance diagram of Ni-MOF and NiMn-MOF catalysts prepared in the examples of the present invention, wherein a is the urea degradation performance diagram of Ni-MOF, and b is the urea degradation performance diagram of NiMn-MOF;

Figure 10 is the urea degradation performance diagram of the Pt _NC /NiMn-MOF catalyst prepared in the examples of the present invention, where a is the urea degradation performance diagram of Pt/NiMn-MOF, b is Pt _NC /NiMn-MOF, NiMn-MOF, and Performance comparison chart of urea degradation rate of Ni-MOF catalyst.

Detailed ways

The advantages and characteristics of the present disclosure, and methods for achieving them will become apparent with reference to the following embodiments together with the accompanying drawings. However, the embodiments should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

If not defined otherwise, all terms (including technical and scientific terms) in this specification can be defined as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be construed to have meanings consistent with their meanings in the context of this disclosure and related art, and will be carried out in an unidealized or overly formal sense interpretation, unless clearly defined herein.

The chemical reagents adopted in the present invention, unless otherwise specified, are of analytical grade, purchased from the market, and the concentration of ethanol used is 99.99%.

A bimetallic MOF anchored Pt nanocluster catalyst provided by the present invention, as shown in Figure 2, the catalyst is a Pt _NC /NiMn-MOF nanomaterial, and the nanomaterial presents a monoclinic nickel-based metal in its X-ray diffraction spectrum Organic framework (Ni-MOF) structure, the corresponding XRD diffraction angle 2θ ranges from 5° to 50°, and the obvious XRD diffraction peaks appearing at 2θ angles of 8.9°, 15.5°, 28.3° and 30.6° correspond to NiMn - (200), (400), (20-2) and (311) crystal planes in the MOF structure.

Example 1

The simple two-step synthesis of a bimetallic MOF-anchored Pt nanocluster catalyst is shown in Figure 1, which specifically includes the following steps:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt Ni(NO ₃ ) ₂ ·6H ₂ O, 0.8 mmol metal manganese salt Mn(NO ₃ ) ₂ ·4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ Add to the solvent, the solvent is composed of 15 mL ethanol, 20 mL N, N-dimethylformamide and 5 mL deionized water, stir well to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 120 °C for 12 h;

Step (4): washing the foam with nickel alcohol and drying it in vacuum to obtain the NiMn-MOF precursor.

Step (5): Place the obtained NiMn-MOF precursor in 10 mL of 1 mg/mL chloroplatinic acid solution, react in a dark environment at room temperature for 1 h, then wash the reacted nickel foam with alcohol and dry it in vacuum to obtain the obtained The bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterials, that is, Pt _NC /NiMn-MOF.

The drying temperature for vacuum drying in step (4) and step (5) was 60 °C, and the drying time was 8 h.

In this example, a bimetallic MOF-anchored Pt nanocluster catalyst was synthesized in two steps using a simple hydrothermal plus room temperature wet chemical etching method, which provided a synthetic reference for MOF structure-anchored nanoclusters; the synthesized materials It has dual functions of HER and UOR, and can be applied to industrial high-current electrolysis of water to produce hydrogen; the application for urea oxidation is mainly urea degradation test.

Figure 1 is a simple schematic diagram of the synthesis of MOF-anchored Pt nanoclusters. Pt _NC /NiMn-MOF nanocomposites were synthesized by a simple two-step synthesis method of hydrothermal plus room temperature wet chemical etching.

Figure 2 is the XRD of NiMn-MOF and Pt _NC /NiMn-MOF prepared in this example. It can be found from the figure that, except for the X-ray diffraction peak of NiMn-MOF, there is no X-ray diffraction peak of any metal Pt , it can be speculated that Pt is not supported on NiMn-MOF in the form of nanoparticles. It can be seen from Figure 3 that the main chemical components of NiMn-MOF are nickel, manganese, carbon and oxygen, and its corresponding micro-nano morphology is a self-supporting two-dimensional porous nanosheet structure. Figure 4 is a scanning electron microscope image of the Pt _NC /NiMn-MOF nanomaterial prepared in this example, and it is found that its main chemical components are platinum, nickel, manganese, carbon and oxygen, and the loading of Pt does not change the NiMn-MOF precursor Therefore, it can be speculated that the existence of Pt in the MOF precursor may be nanocluster doping. Fig. 5 is a dark-field scanning transmission electron microscope (HAADF-STEM) photograph of the Pt _NC /NiMn-MOF nanomaterial prepared in this example. In general, the brightness of each metal atom in the HAADF mode is proportional to the 1.8th power of the corresponding atomic number, and the atomic number of the Pt atom in this system is the largest, so the Pt atom and the Ni, Mn, O, etc. in the NiMn-MOF contrast would be brighter than the bottom atoms. Therefore, the bright spots marked with circles in Figure 5b are Pt clusters, that is, Pt exists in the form of nanoclusters in the catalyst.

Example 2

The simple two-step synthesis of a bimetallic MOF-anchored Pt nanocluster catalyst is shown in Figure 1, which specifically includes the following steps:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt Ni(NO ₃ ) ₂ ·6H ₂ O, 0.8 mmol metal manganese salt Mn(NO ₃ ) ₂ ·4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ Add to the solvent, the solvent is composed of 15 mL ethanol, 20 mL N,N-dimethylformamide and 5 mL deionized water, stir well to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 140 °C for 12 h;

Step (4): washing the foam with nickel alcohol and drying it in vacuum to obtain the NiMn-MOF precursor.

Step (5): The obtained NiMn-MOF precursor was placed in 10 mL of 2 mg/mL chloroplatinic acid solution, and reacted in a dark environment at room temperature for 1 h, and then the reacted nickel foam was washed with alcohol and dried in vacuum to obtain the obtained The bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterials, that is, Pt _NC /NiMn-MOF.

The drying temperature in step (4) and step (5) is 60 °C, and the drying time is 8 h.

Example 3

The simple two-step synthesis of a bimetallic MOF-anchored Pt nanocluster catalyst is shown in Figure 1, which specifically includes the following steps:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt Ni(NO ₃ ) ₂ ·6H ₂ O, 0.8 mmol metal manganese salt Mn(NO ₃ ) ₂ ·4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ Add to the solvent, the solvent is composed of 15 mL ethanol, 20 mL N, N-dimethylformamide and 5 mL deionized water, stir well to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 160 °C for 12 h;

Step (4): washing and drying the nickel foam to obtain the NiMn-MOF precursor.

Step (5): The obtained NiMn-MOF precursor was placed in 10 mL of 3 mg/mL chloroplatinic acid solution, and reacted in a dark environment at room temperature for 1 h, and then the reacted nickel foam was washed with alcohol and dried in vacuum to obtain the obtained The bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterials, that is, Pt _NC /NiMn-MOF.

The drying temperature in step (4) and step (5) is 60 °C, and the drying time is 8 h.

Example 4

A method for preparing a bimetallic MOF-anchored Pt nanocluster catalyst, specifically comprising the steps of:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt Ni(NO ₃ ) ₂ ·6H ₂ O, 0.8 mmol metal manganese salt Mn(NO ₃ ) ₂ ·4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ Add to the solvent, the solvent is composed of 15 mL ethanol, 20 mL N,N-dimethylformamide and 5 mL deionized water, stir well to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 120 °C for 12 h;

Step (4): The NiMn-MOF precursor was obtained by washing the foam with nickel alcohol and drying it in vacuum (the drying temperature was 60 °C and the drying time was 8 h).

Step (5): Place the obtained NiMn-MOF precursor in 10 mL of 2 mg/mL chloroplatinic acid solution, react in a dark environment at room temperature for 1 h, and then wash the reacted nickel foam with alcohol and dry it in vacuum (the drying temperature is 60 °C, and the drying time is 8h)), the bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterial, that is, Pt _NC /NiMn-MOF, can be obtained.

Example 5

A method for preparing a bimetallic MOF-anchored Pt nanocluster catalyst, specifically comprising the steps of:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt NiCl ₂ 6H ₂ O, 0.8 mmol metal manganese salt MnCl ₂ ∙ 4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ were added to the solvent, and the solvent consisted of 15 mL Ethanol, 20 mL N,N-dimethylformamide and 5 mL deionized water, stirred evenly to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 120 °C for 24 hours;

Step (4): washing the foam with nickel alcohol and drying it in vacuum to obtain the NiMn-MOF precursor.

Step (5): Place the obtained NiMn-MOF precursor in 10 mL of 1 mg/mL chloroplatinic acid solution, react in a dark environment at room temperature for 1 h, then wash the reacted nickel foam with alcohol and dry it in vacuum to obtain the obtained The bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterials, that is, Pt _NC /NiMn-MOF.

The drying temperature for vacuum drying in step (4) and step (5) was 60 °C, and the drying time was 8 h.

Example 6

A method for preparing a bimetallic MOF-anchored Pt nanocluster catalyst, specifically comprising the steps of:

Step (1): Pretreatment of nickel foam NF, first ultrasonic in 3 M hydrochloric acid for 15 minutes, then in ultrapure water for 10 minutes, and finally in ethanol for 5 minutes, and then air-dried for later use;

Step (2): 1 mmol metal nickel salt NiSO ₄ 6H ₂ O, 0.8 mmol metal manganese salt MnSO ₄ 4H ₂ O and 1 mmol teredibenzoic acid C ₈ H ₆ O ₄ were added to the solvent, and the solvent consisted of 15 mL ethanol , 20 mL of N,N-dimethylformamide and 5 mL of deionized water, and stir well to form an initial mixed solution;

Step (3): Transfer the initial mixed solution and nickel foam to a 100 ml polytetrafluoroethylene reactor, and react at 120 °C for 24 hours;

Step (4): washing the foam with nickel alcohol and drying it in vacuum to obtain the NiMn-MOF precursor.

Step (5): The obtained NiMn-MOF precursor was placed in 10 mL of 3 mg/mL chloroplatinic acid solution, and reacted in a dark environment at room temperature for 1 h, and then the reacted nickel foam was washed with alcohol and dried in vacuum to obtain the obtained The bimetallic NiMn-MOF-anchored Pt nanocluster catalytic nanomaterials, that is, Pt _NC /NiMn-MOF.

The drying temperature for vacuum drying in step (4) and step (5) was 60 °C, and the drying time was 8 h.

The bifunctional Pt _NC /NiMn-MOF composite nanomaterial prepared in Example 1 of the present invention was tested for HER catalytic activity and UOR catalytic activity, and was used for urea degradation to test its urea degradation performance.

(1) The HER catalytic activity of the prepared catalyst was tested by a three-electrode system

Take the Pt _NC /NiMn-MOF prepared in the example (cut to a size of 1 cm×1 cm) as the working electrode, the Pt electrode as the auxiliary electrode (if the current is too large, the carbon rod will corrode and fall off), and the Hg/HgO electrode as the reference electrode , prepare 1 mol/L KOH (100mL) as the electrolyte, and test the HER catalytic performance under high current conditions.

It can be seen from Figure 6a that the overpotential of the Pt _NC /NiMn-MOF prepared in the example as a HER catalyst driving a current density of 100 mA cm ^-2 is only 56 mV. It can be seen from Figure 6b that the HER catalytic activity of Pt _NC /NiMn-MOF at high current density is comparable to or even better than that of commercial Pt/C, which is an expansion of the HER hydrogen production material system for industrial applications. A new research idea is provided. Considering that the introduction of Pt clusters greatly improves the HER catalytic activity of NiMn-MOF, it is indirectly proved that Pt clusters are the main active species of HER. In addition, the HER catalytic properties of Ni-MOF and NiMn-MOF are similar, and in To a certain extent, it reflects that the Ni and Mn sites are not the real active sites of HER, and they mainly play a synergistic role as a carrier. In addition, it can be seen from Figure 8a that the LSV performance of Pt _NC /NiMn-MOF did not change much after 10,000 CV cycles in the HER process, indicating that its stability is better, which further proves that Pt _NC /NiMn-MOF has a good performance in the oriented The field of hydrogen production by industrial electrolysis of water has great potential.

In Figure 6 to Figure 7, nickel foam (NF): 1 cm × 1 cm, purchased from CyberMaterials.com; ruthenium dioxide (RuO ₂ ): McLean; Ni-MOF, NiMn-MOF - used in this example The precursor was prepared under the synthesis conditions of 120 °C and 12 h by the method, and the difference is that the types and ratios of metal sources added are different. Pt _NC /NiMn-MOF is a nanomaterial of Pt single-atom-loaded MOF prepared by using NiMn-MOF as a precursor and using room temperature wet chemical etching.

(2) The UOR catalytic activity of the prepared catalyst was tested by a three-electrode system

Take the Pt _NC /NiMn-MOF (cut to 1 cm×1 cm size) prepared in the example as the working electrode, and then use the graphite carbon rod and the Hg/HgO electrode as the auxiliary electrode and reference electrode respectively to prepare 100 mL 1 mol/ L KOH + 0.33 mol/L urea was used as the electrolyte to test the electrocatalytic urea oxidation performance.

It can be seen from Figure 7a and Figure 7b that the UOR catalytic performance of Pt _NC /NiMn-MOF is the best, and its UOR driving voltage at 200 mA cm ^-2 and 300 mA cm ^-2 current density is 1.34 V, respectively and 1.35 V, much lower than NiMn-MOF, Ni-MOF, and commercial _RuO2 catalysts. Further, by comparing the LSV polarization curves in Figure 7a, it can be seen that Mn doping can greatly improve the UOR catalytic performance of Ni-based two-dimensional MOF, which may be attributed to the regulation of the electronic structure of Ni-MOF by high-valent Mn doping, optimizing the Its adsorption and desorption of intermediates in the oxidation process of urea. In addition, the introduction of Pt clusters can further create a synergistic effect with NiMn-MOF to increase the conductivity and catalytic activity of MOF supports. It can be seen from Fig. 8b that the LSV polarization curve of Pt _NC /NiMn-MOF undergoes little change after 1000 CV cycles during the UOR process, proving that its urea oxidation stability is better. As we all know, the stability of MOF material systems has always been the core issue in the field of catalysis, whether it is for basic research or for industrial applications. In this case, the catalytic activity of Ni-based two-dimensional MOF And the stability is greatly improved, which provides new insights for the development, design and application of MOF-based materials.

(3) The urea degradation performance of the prepared catalyst was tested by two electrodes

Two-electrode electrodegradation test was taken for urea degradation, in which the cathode and anode were self-supporting Pt _NC /NiMn-MOF, or NiMn-MOF or Ni-MOF nanomaterials (4 cm×4 cm), and then prepared 100 mL 1 mol/ L KOH + 0.33mol/L urea solution was used as the electrolyte, and the degradation performance of urea was tested and compared with this system.

Figures 9a-b and Figures 10a-b are performance graphs of the urea degradation test. It can be seen from Figure 9a-b and Figure 10a-b that the bifunctional Pt _NC /NiMn-MOF composite nanomaterial prepared in the example is used as a catalytic electrode to electrocatalytically degrade the urea-rich alkaline electrolyte. After three hours The degradation rate of urea in this system can reach 96.1%, and its performance of degrading urea is much better than that of _NiMn -MOF and Ni-MOF. The treatment of urea-rich wastewater in China provides a new strategy.

To sum up, the above-mentioned embodiments are only examples for clearly illustrating the application, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the protection scope of the claims of this patent application.

Claims (10)

1. A bimetallic MOF anchored Pt nanocluster catalyst is characterized in that the catalyst is Pt _NC A NiMn-MOF nanomaterial, which in its X-ray diffraction spectrum exhibits a monoclinic nickel-based metal organic framework (Ni-MOF) structure, the corresponding XRD diffraction angles 2 theta range from 5 DEG to 50 DEG, wherein the distinct XRD diffraction peaks at the positions of 8.9 DEG, 15.5 DEG, 28.3 DEG and 30.6 DEG of 2 theta angle respectively correspond to the (200), (400), (20-2) and (311) crystal planes in the NiMn-MOF structure.

2. Preparation method of bimetallic MOF (metal organic framework) anchored Pt nanocluster catalyst which is Pt _NC /NiMn-MOF, the method is as follows: taking metal nickel and manganese as metal nodes and terephthalic acid as the main componentGrowing the NiMn-MOF precursor on foam nickel in situ by taking acid as an organic ligand, and loading the Pt nanocluster on the surface of the NiMn-MOF precursor by utilizing a room-temperature wet chemical etching method to obtain Pt _NC the/NiMn-MOF composite nanometer material.

3. The method of claim 2, comprising the steps of:

step (1): pretreating foamed nickel;

step (2): adding metal nickel salt, metal manganese salt and terephthalic acid into a solvent, and dissolving

The agent consists of ethanol, N-dimethylformamide and deionized water, and is uniformly stirred to obtain an initial mixed solution;

and (3): transferring the initial mixed solution and the foamed nickel into a polytetrafluoroethylene high-pressure reaction kettle for hydrothermal reaction, preferably, the reaction temperature of the hydrothermal reaction is 120-160 ℃, and the reaction time is 12-24 hours;

and (4): taking out the reacted foam nickel, washing with alcohol, and vacuum drying to obtain the final product

A bimetallic organic framework NiMn-MOF precursor;

and (5): immersing the resulting NiMn-MOF precursor in a quantity of chloroplatinic acid solution, and a chamber

Reacting for 1 h in a dark and warm environment, and then carrying out alcohol washing and vacuum drying on the reacted foam nickel to obtain Pt _NC The NiMn-MOF nano material is preferably prepared by a chloroplatinic acid solution with the concentration of 1-3 mg/mL.

4. The method according to claim 3, wherein in the step (1), the pretreatment is carried out by: immersing foamed nickel with the size of 2 cm multiplied by 3 cm in 3 mol/L hydrochloric acid for ultrasonic treatment for 15 minutes, then performing ultrasonic treatment in ultrapure water for 10 minutes, finally performing ultrasonic treatment in ethanol for 5 minutes, and naturally drying for later use.

5. The method according to claim 3, wherein the metallic nickel salt in step (2) is one of nickel nitrate, nickel sulfate and nickel chloride, and the metallic manganese salt is one of manganese nitrate, manganese sulfate and manganese chloride.

6. The preparation method according to claim 3, wherein in the step (2), the molar ratio of the metal nickel salt to the metal manganese salt to the terephthalic acid in the synthesis of the MOF precursor is (0.1 to 1.0): (0.1 to 1.0): (0.1 to 1.0).

7. The preparation method according to claim 3, wherein in the step (2), the volume ratio of the solvent N, N-dimethylformamide to ethanol to deionized water is 4:3:1.

8. the method according to claim 3, wherein the drying temperature of the vacuum drying in the steps (4) and (5) is 60 ℃ and the drying time is 8 hours.

9. Pt according to claim 1 _NC NiMn-MOF nano material or Pt prepared by using preparation method of any one of claims 2 to 9 _NC Use of/NiMn-MOF nanomaterials as electrocatalysts.

10. Use according to claim 9, wherein the electrocatalyst is used for high current electrolysis of water for hydrogen production, urea oxidation or urea degradation.

Images