CoZn bimetallic catalyst, preparation method thereof, hydrogen evolution electrode and electrolyzer

Abstract

This invention relates to the field of hydrogen production through water electrolysis, and discloses a CoZn bimetallic catalyst, its preparation method, a hydrogen evolution electrode, and an electrolyzer. The X-ray powder diffraction pattern of the catalyst exhibits characteristic peaks at 2θ of 25.94±0.18°, 44.16±0.18°, 51.44±0.18°, and 76.26±0.18°. The content of Co and Zn in the catalyst is 36.3-42.7 wt% and 0.03-5.28 wt%, respectively. The average particle size of the catalyst is 90-110 nm. The suitable particle size of this catalyst is beneficial for preparing a structurally stable electrode material, enabling it to maintain constant stability under long-term high-current conditions. The suitable catalyst size combined with an appropriate catalyst layer structure results in a hydrogen evolution electrode exhibiting excellent activity and efficiency.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by water electrolysis, specifically to a CoZn bimetallic catalyst, its preparation method, hydrogen evolution electrode, and electrolyzer. Background Technology

[0002] In comparison, water electrolysis for hydrogen production uses water as the electrolysis raw material. During the electrolysis process, hydrogen and oxygen are generated at the cathode and anode, respectively, without producing any pollutants. This technology is considered green hydrogen technology.

[0003] Membrane electrodes (MEAs) are the core of membrane electrolyzers, crucial for the efficiency and cycle stability of hydrogen production from water electrolysis. In recent years, researchers have devoted considerable effort to the development of electrode materials, particularly focusing on improving the performance and stability of catalytic materials while reducing precious metal content. However, research on transitioning electrode materials from three-electrode systems to electrode structures with good catalytic activity and stability suitable for electrolyzers is limited. It has been shown that most catalysts developed in the laboratory fail to produce the expected catalytic electrodes. The particle size of the coating liquid component in the electrode material is highly correlated with the surface morphology and porosity of the electrode, thus affecting the hydrogen production performance from water electrolysis. When the catalyst particle size is large, the prepared electrode material is non-uniform and has poor stability, making the electrode surface prone to detachment during electrolysis. When the catalyst particle size is small, the electrode material has a more uniform surface morphology, but it is prone to forming a dense structure, which is detrimental to the contact between active sites and the electrolyte, as well as rapid gas desorption. Therefore, preparing catalysts of suitable size, combined with appropriate catalytic layer structures, is crucial for obtaining structurally stable and efficient electrodes, significantly improving the performance of the electrolyzer. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of poor stability of hydrogen evolution electrodes in alkaline membrane electrolyzer systems in the prior art, and to provide a CoZn bimetallic catalyst, its preparation method, hydrogen evolution electrode, and electrolyzer. The catalyst has a suitable particle size, which is beneficial for preparing structurally stable electrode materials, enabling them to maintain constant stability under long-term high-current conditions.

[0005] To achieve the above objectives, the first aspect of the present invention provides a CoZn bimetallic catalyst, wherein the X-ray powder diffraction pattern of the catalyst has characteristic peaks at 2θ of 25.94±0.18°, 44.16±0.18°, 51.44±0.18°, and 76.26±0.18°; the contents of Co and Zn in the catalyst are 36.3-42.7 wt% and 0.03-5.28 wt%, respectively; and the average particle size of the catalyst is 90-110 nm.

[0006] A second aspect of this invention provides a method for preparing a CoZn bimetallic catalyst, characterized in that the preparation method includes the following steps:

[0007] S1. In the presence of a solvent, a cobalt source, a zinc source, and a nitrogen-containing organic ligand are mixed and reacted to obtain a precursor; wherein the weight ratio of the cobalt source, the zinc source, and the nitrogen-containing organic ligand is (1.5-3):1:(4-8); and the amount of solvent used is 25-35 mL, based on a total weight of 1 g of the cobalt source, the zinc source, and the nitrogen-containing organic ligand.

[0008] S2. The precursor is heated in the presence of a protective gas to obtain a CoZn bimetallic catalyst.

[0009] A third aspect of the present invention provides a CoZn bimetallic catalyst prepared by the preparation method provided by the present invention.

[0010] A fourth aspect of the present invention provides a hydrogen evolution electrode, wherein the hydrogen evolution electrode is obtained by spraying a slurry onto the surface of a gas diffusion layer; the slurry comprises a CoZn bimetallic catalyst provided by the present invention.

[0011] A fifth aspect of the present invention provides an electrolytic cell, wherein the cathode of the electrolytic cell is the hydrogen evolution electrode provided by the present invention.

[0012] The beneficial effects of the present invention through the above technical solution are as follows:

[0013] By controlling the ratio of cobalt source, zinc source, and nitrogen-containing organic ligand, a CoZn-ZIF precursor, upon heating, yields a catalyst with suitable contents of Co, Zn, N, and C elements. By adjusting the solution concentration (solvent amount) during precursor preparation, as well as the ratio of cobalt source, zinc source, and nitrogen-containing organic ligand, the size of the CoZn-ZIF precursor is maintained at 90-110 nm. The catalyst formed after heating the precursor has a size of 90-110 nm, indicating a suitable catalyst size. Using this catalyst as the active component, a slurry is prepared. By selecting the appropriate amounts of each component in the electrode slurry, it is sprayed onto the surface of the gas diffusion layer to obtain a highly efficient and stable hydrogen evolution electrode for the hydrogen evolution reaction, improving the overall efficiency and stability of alkaline membrane water electrolysis for hydrogen production. Attached Figure Description

[0014] Figure 1 This is a SEM image of the CoZn-ZIF precursor obtained in Example 1 of this invention;

[0015] Figure 2 This is a SEM image of the catalyst prepared in Example 1 of this invention;

[0016] Figure 3This is the X-ray powder diffraction pattern of the catalyst prepared in Example 1 of this invention;

[0017] Figure 4 This is a SEM image of the hydrogen evolution electrode prepared in Example 1 of the present invention;

[0018] Figure 5 This is a polarization curve of the hydrogen evolution electrode prepared in Example 1 of the present invention;

[0019] Figure 6 This is a stability curve of the hydrogen evolution electrode prepared in Example 1 of the present invention;

[0020] Figure 7 This is a SEM image of the CoZn-ZIF precursor prepared in Comparative Example 1 of this invention;

[0021] Figure 8 This is a SEM image of the CoZn-ZIF precursor obtained in Comparative Example 2 of this invention;

[0022] Figure 9 This is a SEM image of the CoZn-ZIF precursor prepared in Comparative Example 3 of this invention. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of this invention provides a CoZn bimetallic catalyst, wherein the X-ray powder diffraction pattern of the catalyst has characteristic peaks at 2θ of 25.94±0.18°, 44.16±0.18°, 51.44±0.18° and 76.26±0.18°; the contents of Co and Zn in the catalyst are 36.3-42.7 wt% and 0.03-5.28 wt%, respectively; and the average particle size of the catalyst is 90-110 nm.

[0025] The X-ray powder diffraction pattern of the CoZn bimetallic catalyst of this invention shows a diffraction peak for the carbon component at 2θ of 25.94 ± 0.18°, and characteristic peaks for CoN at 44.16 ± 0.18°, 51.44 ± 0.18°, and 76.26 ± 0.18°, indicating that the catalyst is a C / N-doped CoZn bimetallic catalyst material. The Zn content in the catalyst is low, and the material has moderate crystallinity; therefore, no obvious Zn-corresponding structure was detected. The average particle size of this bimetallic catalyst material is 90-110 nm, which is suitable for preparing a structurally stable electrode material, allowing it to maintain constant stability under long-term high-current conditions. The suitable catalyst size combined with an appropriate catalytic layer structure results in a hydrogen evolution electrode exhibiting excellent activity and efficiency. Furthermore, a large number of carbon nanotube structures are generated on the catalyst surface. These carbon nanotube structures can increase the specific surface area of ​​the material, reduce resistivity, and enhance the catalytic stability of the material.

[0026] According to the present invention, preferably, the content of nitrogen element in the catalyst is 3.55-3.72 wt%; and / or, the content of carbon element in the catalyst is 50.8-59.5 wt%.

[0027] To further improve the activity and efficiency of the prepared hydrogen evolution electrode, preferably, the catalyst has an average particle size of 97-103 nm.

[0028] A second aspect of this invention provides a method for preparing a CoZn bimetallic catalyst, characterized in that the preparation method includes the following steps:

[0029] S1. In the presence of a solvent, a cobalt source, a zinc source, and a nitrogen-containing organic ligand are mixed and reacted to obtain a precursor; wherein the weight ratio of the cobalt source, the zinc source, and the nitrogen-containing organic ligand is (1.5-3):1:(4-8); and the amount of solvent used is 25-35 mL, based on a total weight of 1 g of the cobalt source, the zinc source, and the nitrogen-containing organic ligand.

[0030] S2. The precursor is heated in the presence of a protective gas to obtain the CoZn bimetallic catalyst.

[0031] This invention uses cobalt and zinc as framework nodes, coordinating with nitrogen-containing organic ligands to obtain a CoZn bimetallic zeolite imidazole ester framework precursor (CoZn-ZIF precursor). Heating (annealing) this precursor in the presence of a protective gas carbonizes the nitrogen-containing organic ligands, resulting in a CoZn bimetallic catalyst with C / N doping. Both Co and Zn exist in metallic form and are interconnected through the C and N components in the structure, yielding a C / N-doped CoZn bimetallic catalyst with surface-loaded carbon nanotubes. By controlling the ratio of cobalt source, zinc source, and nitrogen-containing organic ligand, the CoZn-ZIF precursor, upon heating, yields catalysts with suitable contents of Co, Zn, N, and C. By adjusting the solution concentration (solvent amount) during precursor preparation, as well as the ratio of cobalt source, zinc source, and nitrogen-containing organic ligand, the size of the CoZn-ZIF precursor is maintained at 90-110 nm. The precursor is heated, and the nitrogen-containing organic ligands therein are carbonized to form a catalyst with a size of 90-110 nm. The catalyst size is suitable. The catalyst is used as the active component to prepare a slurry, which is then sprayed onto the surface of the gas diffusion layer to obtain a highly efficient and stable hydrogen evolution electrode.

[0032] According to the present invention, preferably, the cobalt source is selected from water-soluble cobalt salts, more preferably from cobalt chloride and / or cobalt nitrate, and more preferably from cobalt nitrate.

[0033] According to the present invention, preferably, the zinc source is selected from water-soluble zinc salts, more preferably from at least one of zinc chloride and zinc nitrate, and more preferably zinc nitrate.

[0034] According to the present invention, preferably, the nitrogen-containing organic ligand is selected from at least one of imidazole and / or 2-methylimidazole, and more preferably 2-methylimidazole.

[0035] This invention does not have particular requirements regarding the type of solvent used in the reaction of the cobalt source, zinc source, and nitrogen-containing organic ligand, as long as the reaction of the cobalt source, zinc source, and nitrogen-containing organic ligand proceeds smoothly. Preferably, the solvent is selected from C1-C4 monohydric alcohols, and more preferably methanol.

[0036] Using 2-methylimidazole as the nitrogen-containing organic ligand simplifies the catalyst preparation process, enabling the synthesis of CoZn-ZIF precursors with regular morphology at room temperature. Preferably, the reaction temperature is 20-30℃ and the reaction time is 20-30 h.

[0037] To ensure a more uniform mixture of the cobalt source, zinc source, and 2-methylimidazole, thereby facilitating a smoother reaction, the preparation method of the CoZn-ZIF precursor preferably includes the following steps:

[0038] S1. The cobalt source, zinc source and solvent are mixed in a first step to obtain mixture A;

[0039] S2. Mix 2-methylimidazole and solvent a second time to obtain mixture B;

[0040] S3. The mixture A and the mixture B are mixed for a third time and the reaction is carried out to obtain the precursor.

[0041] The solvents in S1 and S2 are each independently selected from C1-C4 monohydric alcohols. The solvents in S1 and S2 can be the same or different. Preferably, the solvents in S1 and S2 are both methanol.

[0042] To ensure a more uniform mixture of the cobalt source, zinc source, and 2-methylimidazole, thereby facilitating a smoother reaction, preferably, based on a total amount of 1g of the cobalt and zinc sources, the amount of solvent used in S1 is 35-50mL; and based on a 1g amount of 2-methylimidazole, the amount of solvent used in S2 is 18-25mL.

[0043] To obtain a pure precursor, S3 further includes: after the reaction, washing and drying the solid product to obtain the precursor. A solvent that does not damage the catalyst morphology and structure and is easily volatile is selected for washing, such as anhydrous ethanol.

[0044] In this invention, the cobalt source and the zinc source may exist with or without bound water. Cobalt nitrate may be Co(NO3)2·6H2O, and zinc nitrate may be Zn(NO3)2·6H2O. When selecting the amount of solvent, cobalt nitrate and zinc nitrate are used in the form of Co(NO3)2·6H2O and Zn(NO3)2·6H2O, respectively.

[0045] Under the aforementioned conditions, CoZn-ZIF precursors with uniform particle size (average particle size of 90-110 nm) and regular morphology can be prepared.

[0046] According to the present invention, preferably, in S2, the heating conditions include: heating to 700-900°C at a rate of 3-8°C / min, and maintaining at 700-900°C for 1.5-2.5 hours.

[0047] According to the present invention, preferably, the protective gas is selected from nitrogen and / or an inert gas, more preferably from at least one of nitrogen, argon and helium, and more preferably from argon.

[0048] To fully remove the remaining gases in the system and avoid introducing impurities during the annealing process, according to a preferred embodiment of the present invention, argon gas is first introduced at a flow rate of 25-35 mL / min for 1.5-2.5 h to fully remove the remaining gases in the system; then, argon gas is introduced at a flow rate of 15-25 mL / min, and the temperature is raised to 700-900 °C at a rate of 3-8 °C / min, and the temperature is maintained at 700-900 °C for 1.5-2.5 h for heating, and then naturally cooled to room temperature.

[0049] A third aspect of the present invention provides a CoZn bimetallic catalyst prepared by the preparation method provided by the present invention.

[0050] A fourth aspect of the present invention provides a hydrogen evolution electrode, wherein the hydrogen evolution electrode is obtained by spraying a slurry onto the surface of a gas diffusion layer; the slurry comprises a CoZn bimetallic catalyst provided by the present invention.

[0051] The gas diffusion layer is a crucial basic material for manufacturing membrane electrodes. During the electrochemical reaction in the battery, the gas diffusion layer not only provides a transport channel for gaseous reactants and liquid water but also a conduction channel for electricity and heat. This invention does not have particular requirements for the material of the gas diffusion layer; conventional gas diffusion layers used in the art for preparing membrane electrodes can be selected. Preferably, the material of the gas diffusion layer is selected from at least one of carbon paper, nickel foam, and nickel felt, and more preferably carbon paper.

[0052] According to the present invention, preferably, the slurry further includes an anionic polymer and a solvent.

[0053] According to the present invention, preferably, the weight ratio of the catalyst to the anionic polymer in the slurry is (2.33-10):1.

[0054] To further improve the morphology and pore size of the prepared membrane electrode material, and to enable the hydrogen evolution electrode to exhibit excellent hydrogen evolution performance and long-lasting stability in alkaline membrane electrolyzer hydrogen production, preferably, the concentration of the anionic polymer in the slurry is 1-4.29 mg / mL.

[0055] The CoZn bimetallic catalyst of this invention has an average particle size of 90-110 nm, which is suitable for preparing structurally stable electrode materials and ensuring their long-term stability under high-current conditions. Furthermore, by selecting the appropriate amounts of each component in the electrode spraying slurry, a highly efficient and stable gas diffusion electrode was obtained for the hydrogen evolution reaction, improving the overall efficiency and stability of alkaline membrane water electrolysis for hydrogen production.

[0056] This invention does not impose any particular limitation on the type of anionic polymer, and any anionic polymer conventionally used in membrane electrodes in the art can be used. This invention also does not impose any particular limitation on the weight-average molecular weight of the anionic polymer, as long as it meets the requirements for use in membrane electrodes. For example, the anionic polymer can be one or more of A5-HCO3, anionic polyacrylamide (PAM), and sodium polyacrylate (PAAS), preferably A5-HCO3.

[0057] When preparing the slurry, the anionic polymer can be added in the form of a mixture of the anionic polymer and a solvent. For example, A5-HCO3 uses ethanol as a solvent with a mass concentration of 5 wt%. In this invention, the amount of anionic polymer used is calculated in solvent-free form.

[0058] This invention does not impose any particular requirements on the type of solvent used in the slurry; it can be any solvent conventionally used in the art for preparing spray slurries for hydrogen evolution electrodes. Preferably, the solvent is selected from C1-C4 monohydric alcohols, and more preferably isopropanol.

[0059] According to the present invention, preferably, the surface area of ​​the hydrogen evolution electrode is 1 cm². 2 The catalyst loading is estimated to be 1-2 mg. A loading within this range allows for effective utilization of the catalyst's active surface area; otherwise, a lower loading reduces the catalyst's active surface area, while an excessively high loading keeps the active surface area essentially unchanged, but hinders electron conduction, thus affecting catalytic performance.

[0060] According to the present invention, preferably, the surface area of ​​the hydrogen evolution electrode is 2-8 cm². 2 A surface area within this range for the hydrogen evolution electrode facilitates the rapid escape of the generated gas, thereby increasing the hydrogen production rate.

[0061] A fifth aspect of the present invention provides an electrolytic cell, wherein the cathode of the electrolytic cell is the hydrogen evolution electrode provided by the present invention.

[0062] According to the present invention, preferably, the electrolytic cell further includes an oxygen evolution electrode, an anion exchange membrane (AEM), and a current collector.

[0063] The oxygen evolution electrode used in this invention can be a conventional oxygen evolution electrode with high oxygen evolution activity. According to a preferred embodiment of the invention, a NiFe-LDH / NF oxygen evolution electrode is used. In an alkaline membrane electrode system composed of the NiFe-LDH / NF oxygen evolution electrode, this system exhibits good performance.

[0064] According to the present invention, preferably, the thickness of the anion exchange membrane is 20-80 μm, more preferably 35-45 μm.

[0065] The electrolytic cell includes two current collectors. The present invention does not have any particular restrictions on the material of the current collectors, and they can be conventional current collectors in the art, such as stainless steel current collectors.

[0066] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all methods used in the following examples are conventional; the reagents and materials used are commercially available unless otherwise specified. The materials and testing methods involved in each example and comparative example are as follows:

[0067] The NiFe-LDH / NF oxygen evolution electrode is a NiFe bilayer hydroxide grown on nickel foam. The preparation method is as follows: Weigh 0.606 g of ferric nitrate, 0.9 g of urea, and 0.37 g of ammonium fluoride, add 35 ml of deionized water, and stir magnetically for 30 min at room temperature to obtain solution A. Weigh 1 mg of conductive carbon black, 0.09 g of nickel carbonyl powder, and 0.25 g of polyvinylpyrrolidone, add 35 ml of deionized water, and sonicate to dissolve for 30 min to obtain solution B. Mix solutions A and B thoroughly, place the nickel foam in a stainless steel hydrothermal reactor with a polytetrafluoroethylene liner, add the mixed solution, seal, and hydrothermally react at 120 °C for 12 h in an oven. Remove the sample, wash it several times with ethanol and deionized water, and dry it in a vacuum oven at 60 °C for 6 h.

[0068] The mass percentages of Co and Zn in the CoZn bimetallic catalyst were determined using an iCAP 6300 ThermoFisher instrument according to inductively coupled plasma optical emission spectrometry (ICP-OES); the mass percentages of N and C were determined using a Vario microcube elemental analyzer according to the thermal decomposition method.

[0069] Electrochemical performance tests were performed using an IPS 100A electrochemical workstation.

[0070] The following examples illustrate the preparation of the catalyst and the hydrogen evolution electrode.

[0071] Example 1

[0072] S1. Weigh cobalt nitrate and zinc nitrate into a beaker, then add methanol (41.6 mL of methanol for a total of 1 g of cobalt nitrate and zinc nitrate), and stir to dissolve, obtaining solution A. Weigh 2-methylimidazole (the weight ratio of cobalt nitrate, zinc nitrate, and 2-methylimidazole is 2:1:5.5) and add it to a beaker containing the methanol solution (23 mL of methanol for a total of 1 g of 2-methylimidazole), and stir to obtain solution B. Then, under stirring, add solution B to solution A and mix thoroughly. Stir the above solutions at 25°C for 24 h, centrifuge, and wash the product three times with anhydrous ethanol to obtain the CoZn-ZIF precursor material, which is then dried for later use.

[0073] S2. Weigh 2g of dry CoZn-ZIF precursor material into the middle of a vertical furnace. Introduce argon gas at a flow rate of 30mL / min for 2 hours to thoroughly remove remaining gases from the system. Then adjust the argon flow rate to 20mL / min and, under continuous argon gas introduction, slowly heat to 700℃ at a heating rate of 5℃ / min, maintain this temperature for 2 hours, and allow to cool naturally to room temperature to obtain a C / N-doped CoZn bimetallic catalyst. The contents of Co, Zn, N, and C in the catalyst are 41.5wt%, 3.82wt%, 3.64wt%, and 51.2wt%, respectively.

[0074] S3. The catalyst was prepared into a spraying ink using isopropanol as the solvent and an anionic polymer A5-HCO3 was added. The concentrations of the catalyst and A5-HCO3 (A5-HCO3 content is based on solute) in the spraying ink were 10 mg / mL and 2.5 mg / mL, respectively. The prepared solution was ultrasonically dispersed for 1 h. The spraying ink was then sprayed onto the surface of a gas diffusion layer (Toray carbon paper 060, thickness 0.19 mm) to obtain a hydrogen evolution electrode. The electrode area was 4 cm². 2 The catalyst loading was 2 mg cm⁻¹ -2 .

[0075] Example 2

[0076] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the weight ratio of catalyst to A5-HCO3 in the spray ink was different. Specifically, in S3, "the content of A5-HCO3 in the spray ink is 1 mg / mL" was replaced with "the content of A5-HCO3 in the spray ink is 2.5 mg / mL". The hydrogen evolution electrode was then obtained.

[0077] Example 3

[0078] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the content of A5-HCO3 in the spray ink was different. Specifically, in S3, "the content of A5-HCO3 in the spray ink is 4.29 mg / mL" was replaced with "the content of A5-HCO3 in the spray ink is 2.5 mg / mL". The hydrogen evolution electrode was then obtained.

[0079] Example 4

[0080] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the catalyst loading on the hydrogen evolution electrode was different. Specifically, the catalyst loading was 1 mg cm⁻¹. -2 The catalyst loading for "replacement" is 2 mg cm⁻¹ -2 A hydrogen evolution electrode was prepared.

[0081] Example 5

[0082] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the type of gas diffusion layer was different. Specifically, in S3, "Toray carbon paper 060" was replaced with "nickel foam with a thickness of 0.2 mm". The hydrogen evolution electrode was then obtained.

[0083] Example 6

[0084] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the type of gas diffusion layer and the catalyst loading were different. Specifically, in S3, a nickel foam with a thickness of 0.2 mm was used; the catalyst loading was 1 mg / cm³. -2 "Replace Toray Carbon Paper 060; catalyst loading is 2mg cm⁻¹" -2 A hydrogen evolution electrode was prepared.

[0085] Example 7

[0086] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the type of gas diffusion layer and the content of A5-HCO3 in the spray ink were different. Specifically, in S3, "Toray carbon paper 060 with a thickness of 0.2 mm and an A5-HCO3 content of 4.29 mg / mL in the spray ink" were replaced with "Ni foam with a thickness of 0.2 mm and an A5-HCO3 content of 2.5 mg / mL in the spray ink". The hydrogen evolution electrode was thus obtained.

[0087] Example 8

[0088] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the type of gas diffusion layer was different. Specifically, in S3, "0.25 mm thick nickel felt" was used instead of "Toray carbon paper 060". The hydrogen evolution electrode was then obtained.

[0089] Example 9

[0090] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the type of gas diffusion layer and the catalyst loading were different. Specifically, in S3, a nickel felt with a thickness of 0.25 mm was used; the catalyst loading was 1 mg / cm³. -2 "Replace Toray Carbon Paper 060; catalyst loading is 2mg cm⁻¹" -2 A hydrogen evolution electrode was prepared.

[0091] Example 10

[0092] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the type of gas diffusion layer and the content of A5-HCO3 in the spray ink were different. Specifically, in S3, "0.25 mm thick nickel felt; 1 mg / mL A5-HCO3 content in the spray ink" was used instead of "Toray carbon paper 060; 2.5 mg / mL A5-HCO3 content in the spray ink". The hydrogen evolution electrode was then obtained.

[0093] Example 11

[0094] The hydrogen evolution electrode was prepared according to the method in Example 1, except that in S2, "slowly heated to 700°C at a heating rate of 5°C / min" was replaced with "slowly heated to 1000°C at a heating rate of 5°C / min". A catalyst was obtained, and thus the hydrogen evolution electrode was obtained.

[0095] The contents of Co, Zn, N and C in the catalyst are 42.7 wt%, 0.03 wt%, 3.72 wt% and 53.5 wt%, respectively.

[0096] Example 12

[0097] The hydrogen evolution electrode was prepared according to the method in Example 1, except that in S2, "slowly heated to 700°C at a heating rate of 5°C / min" was replaced with "slowly heated to 600°C at a heating rate of 5°C / min". A catalyst was obtained, and thus the hydrogen evolution electrode was obtained.

[0098] The contents of Co, Zn, N and C in the catalyst are 40.3 wt%, 5.28 wt%, 3.55 wt% and 50.8 wt%, respectively.

[0099] Example 13

[0100] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the concentration of A5-HCO3 in the spray ink was different. Specifically, in S3, "the content of A5-HCO3 in the spray ink is 0.53 mg / mL" was replaced with "the content of A5-HCO3 in the spray ink is 2.5 mg / mL". The hydrogen evolution electrode was then obtained.

[0101] Example 14

[0102] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the concentration of A5-HCO3 in the spray ink was different. Specifically, in S3, "the content of A5-HCO3 in the spray ink is 6.67 mg / mL" was replaced with "the content of A5-HCO3 in the spray ink is 2.5 mg / mL". The hydrogen evolution electrode was then obtained.

[0103] Example 15

[0104] The hydrogen evolution electrode was prepared according to the method of Example 1, except that the catalyst loading on the hydrogen evolution electrode was different. Specifically, a catalyst loading of 3 mg / cm³ was used. -2 The catalyst loading for "replacement" is 2 mg cm⁻¹ -2 A hydrogen evolution electrode was prepared.

[0105] Comparative Example 1

[0106] The hydrogen evolution electrode was prepared according to the method in Example 1, except that in S1, "based on a total amount of 1g of cobalt nitrate and zinc nitrate, the amount of methanol is 20.8mL; the weight ratio of cobalt nitrate, zinc nitrate, and 2-methylimidazole is 2:1:2.73" was used instead of "based on a total amount of 1g of cobalt nitrate and zinc nitrate, the amount of methanol is 41.6mL; the weight ratio of cobalt nitrate, zinc nitrate, and 2-methylimidazole is 2:1:5.5". A CoZn-ZIF precursor material was obtained, which in turn yielded a catalyst, and ultimately, the hydrogen evolution electrode.

[0107] The contents of Co, Zn, N and C in the catalyst are 41.8%, 3.87%, 3.56% and 50.9%, respectively.

[0108] Comparative Example 2

[0109] The hydrogen evolution electrode was prepared according to the method in Example 1, except that in S1, "based on a total amount of 1g of cobalt nitrate and zinc nitrate, the amount of methanol is 13.9mL; based on a total amount of 1g of 2-methylimidazole, the amount of methanol is 7.6mL" was replaced with "based on a total amount of 1g of cobalt nitrate and zinc nitrate, the amount of methanol is 41.6mL; based on a total amount of 1g of 2-methylimidazole, the amount of methanol is 23mL". A CoZn-ZIF precursor material was obtained, which in turn yielded a catalyst, and ultimately, the hydrogen evolution electrode.

[0110] The contents of Co, Zn, N and C in the catalyst are 42.2%, 3.95%, 3.61% and 50.3%, respectively.

[0111] Comparative Example 3

[0112] The hydrogen evolution electrode was prepared according to the method in Example 1, except that the weight ratio of cobalt nitrate, zinc nitrate, and 2-methylimidazole was 2:1:2.73 instead of 2:1:5.5. A CoZn-ZIF precursor material was obtained, which in turn led to a catalyst and ultimately the hydrogen evolution electrode.

[0113] The contents of Co, Zn, N and C in the catalyst are 41.7%, 3.88 wt%, 3.6 wt% and 50.8%, respectively.

[0114] Test Example 1

[0115] Scanning electron microscopy was used to examine the Co-ZIF precursor material, Co-based catalyst, and hydrogen evolution electrode; X-ray powder diffraction patterns of the Co-based catalyst were determined using X-ray diffraction.

[0116] The scanning electron microscope image of the CoZn-ZIF precursor prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1It can be seen that the average particle size of the CoZn-ZIF precursor is 100 nm. The scanning electron microscope images of the CoZn-ZIF precursors prepared in Examples 2-15 are shown in the figure. Figure 1 Similarly, the average particle size is in the range of 90-110 nm, not shown in the text. Scanning electron micrographs of the CoZn-ZIF precursors prepared in Comparative Examples 1, 2, and 3 are shown below. Figure 7 , Figure 8 and Figure 9 As shown, by Figure 7 , Figure 8 and Figure 9 It can be seen that the average particle sizes of the CoZn-ZIF precursors prepared in Comparative Examples 1, 2, and 3 are 500 nm, 1 μm, and 110 nm, respectively. Among them, the CoZn-ZIF precursor prepared in Comparative Example 3 has poor particle integrity and uneven particle size.

[0117] The average particle size of the catalyst prepared in Example 1 was determined to be 102 nm using scanning electron microscopy. The average particle sizes of the catalysts prepared in Examples 11 and 12 were 110 nm and 100 nm, respectively (not shown in the text). The average particle sizes of the catalysts prepared in Comparative Examples 1, 2, and 3 were 520 nm, 1.05 μm, and 115 nm, respectively (not shown in the text).

[0118] The scanning electron microscope image of the catalyst prepared in Example 1 is shown below. Figure 2 As shown, by Figure 2 It can be seen that a large number of carbon nanotube structures have been generated on the surface of the material.

[0119] The X-ray powder diffraction pattern of the catalyst prepared in Example 1 is shown below. Figure 3 As shown, by Figure 3 As can be seen, the X-ray powder diffraction peak positions of the catalyst are represented by 2θ angles. The peak at 25.94° represents the diffraction peak of the carbon component in the structure, while the peaks at 44.16°, 51.44°, and 76.26° represent characteristic peaks of the CoN component in the structure, indicating that the catalyst is a C / N-doped CoZn bimetallic material. The scanning electron microscope images of the catalysts prepared in Examples 2-15 are shown below. Figure 1 Similarly, not shown in the text.

[0120] The scanning electron microscope image of the hydrogen evolution electrode prepared in Example 1 of this invention is shown below. Figure 4 As shown, by Figure 4 It can be seen that the catalyst is attached to the substrate surface.

[0121] Test Example 2

[0122] The hydrogen evolution electrodes prepared in the various embodiments and comparative examples were used in alkaline membrane electrolyzers. The effective area of ​​a single cell was 4 cm². 2The electrode assembly consists of an oxygen evolution electrode, a hydrogen evolution electrode, an anion exchange membrane (AEM membrane, brand name PiperION, thickness 40 μm), and two stainless steel current collectors. The AEM membrane was immersed in a 1 mol / L KOH solution at room temperature for 24 h, rinsed with deionized water to remove surface alkali, and then placed between the oxygen evolution electrode and the hydrogen evolution electrode. Stainless steel clamps on both sides of the electrodes were used to clamp them with a force of 4 Nm, and the electrodes were sealed with PTFE gaskets of appropriate thickness. After the electrodes were assembled, a constant current method (10 mA cm⁻¹) was used. -2 5 min; 20 mAcm -2 5 min; 30 mA cm -2 5 min; 40 mA cm -2 5 min; 50 mA cm -2 5 min; 100 mA cm -2 5 min; 200 mA cm -2 5 min; 300 mA cm -2 5 min; 400 mA cm -2 5 min; 500 mA cm -2 Activation was performed (5 min), and then the polarization curve of the electrode was tested, as well as the 500 mA cm⁻¹. -2 The durability of an alkaline exchange membrane water electrolyzer (AEMWE) was evaluated under varying current densities. The AEMWE was tested at 60°C using 1 mol / L KOH as the electrolyte (flow rate 4-8 mL / min). The current density was 500 mA / cm². 2 The cell voltage at that time, and the current density of 500 mA / cm². 2 The results of the average electrode decay rate over 100 hours are shown in Table 1.

[0123] Table 1

[0124] serial number Slot pressure, V Average electrode decay rate, mV / h Example 1 1.845 0.821 Example 2 1.854 0.872 Example 3 1.869 0.851 Example 4 1.868 0.95 Example 5 1.869 0.962 Example 6 1.887 1.103 Example 7 1.879 0.942 Example 8 1.848 0.862 Example 9 1.875 0.874 Example 10 1.859 0.893 Example 11 1.912 1.175 Example 12 1.895 0.874 Example 13 1.868 0.927 Example 14 1.882 0.923 Example 15 1.873 0.981 Comparative Example 1 1.898 1.32 Comparative Example 2 1.928 1.58 Comparative Example 3 1.917 1.46

[0125] The electrode polarization curve obtained in Example 1 is as follows: Figure 5 As shown, by Figure 5 It can be seen that the electrolytic cell system exhibits good performance at a current density of 500 mA / cm². 2 The cell voltage was 1.845V and the current density was 1A / cm². 2 The cell voltage at that time was 1.969V.

[0126] The electrode stability curve obtained in Example 1 is shown below. Figure 6 As shown, by Figure 6 It can be seen that at a current density of 500 mA / cm² 2It exhibited excellent stability during a continuous 100-hour stability test. The average decay rate over 100 hours was 0.821 mV / h.

[0127] The results in Table 1 show that the hydrogen evolution electrodes prepared with the CoZn bimetallic catalysts in Examples 1-15 operate at a current density of 500 mA / cm². 2 The average electrode decay rate was below 1.175 mV / h over 100 hours. Comparative Example 1 changed the ratio and concentration of cobalt source, zinc source and nitrogen-containing organic ligand during precursor preparation; Comparative Example 2 changed the concentration of cobalt source, zinc source and nitrogen-containing organic ligand during precursor preparation; Comparative Example 3 changed the ratio of cobalt source, zinc source and nitrogen-containing organic ligand during precursor preparation. Compared with Examples 1-15, the average electrode decay rate increased, indicating that the catalyst of the present invention can obtain a structurally stable and efficient electrode.

[0128] Furthermore, in Examples 5 and 8, carbon paper was replaced with nickel foam and nickel felt, respectively. Compared with Example 1, the average decay rate of the hydrogen evolution electrodes prepared in Examples 5 and 8 increased. Example 10 differs from Example 2 in that carbon paper was replaced with nickel felt. Compared with Example 2, the average decay rate of the hydrogen evolution electrode prepared in Example 10 increased, indicating that selecting a preferred gas diffusion layer can further improve the stability of the hydrogen evolution electrode. Examples 11 and 12 both changed the calcination temperature of the precursor. Compared with Example 1, the average decay rate of the hydrogen evolution electrodes prepared in Examples 11 and 12 increased, indicating that satisfying the preferred calcination temperature of the precursor can further improve the stability of the hydrogen evolution electrode. Examples 13 and 14 changed the weight ratio of catalyst to anionic polymer in the spray slurry. Compared with Example 1, the average decay rate of the hydrogen evolution electrodes prepared in Examples 13 and 14 increased, indicating that satisfying the preferred weight ratio of catalyst to anionic polymer in the spray slurry can further improve the stability of the hydrogen evolution electrode. Example 15 increased the catalyst loading on the hydrogen evolution electrode. Compared with Example 1, the average decay rate of the hydrogen evolution electrode prepared in Example 15 increased, which shows that the stability of the hydrogen evolution electrode can be further improved when the catalyst loading on the hydrogen evolution electrode meets the preferred conditions.

[0129] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A CoZn bimetallic catalyst, characterized in that, The X-ray powder diffraction pattern of the catalyst exhibits characteristic peaks at 2θ of 25.94±0.18°, 44.16±0.18°, 51.44±0.18°, and 76.26±0.18°; the contents of Co and Zn in the catalyst are 36.3-42.7 wt% and 0.03-5.28 wt%, respectively; the average particle size of the catalyst is 97-103 nm. The catalyst contains 3.55-3.72 wt% nitrogen. The catalyst contains 50.8-59.5 wt% carbon.

2. A method for preparing the CoZn bimetallic catalyst according to claim 1, characterized in that, The preparation method includes the following steps: S1. In the presence of a solvent, a cobalt source, a zinc source, and a nitrogen-containing organic ligand are mixed and reacted to obtain a precursor; wherein the weight ratio of the cobalt source, the zinc source, and the nitrogen-containing organic ligand is (1.5-3):1:(4-8); and the amount of solvent used is 25-35 mL, based on a total weight of 1 g of the cobalt source, the zinc source, and the nitrogen-containing organic ligand. S2. The precursor is heated in the presence of a protective gas to obtain a CoZn bimetallic catalyst.

3. The preparation method according to claim 2, characterized in that, The cobalt source is selected from water-soluble cobalt salts.

4. The preparation method according to claim 3, characterized in that, The cobalt source is selected from cobalt chloride and / or cobalt nitrate.

5. The preparation method according to claim 4, characterized in that, The cobalt source is selected from cobalt nitrate.

6. The preparation method according to claim 2, characterized in that, The zinc source is selected from water-soluble zinc salts.

7. The preparation method according to claim 6, characterized in that, The zinc source is selected from at least one of zinc chloride and zinc nitrate.

8. The preparation method according to claim 7, characterized in that, The zinc source is selected from zinc nitrate.

9. The preparation method according to claim 2, characterized in that, The nitrogen-containing organic ligand is selected from imidazole and / or 2-methylimidazolium.

10. The preparation method according to claim 9, characterized in that, The nitrogen-containing organic ligand is selected from 2-methylimidazole.

11. The preparation method according to claim 2, characterized in that, The solvent is selected from C1-C4 monohydric alcohols.

12. The preparation method according to claim 11, characterized in that, The solvent is methanol.

13. The preparation method according to claim 2, characterized in that, The reaction is carried out at a temperature of 20-30℃ for 20-30 hours.

14. The preparation method according to claim 2, characterized in that, In S2, the heating conditions include: heating to 700-900°C at a rate of 3-8°C / min, and maintaining the temperature at 700-900°C for 1.5-2.5 hours.

15. The preparation method according to claim 2, characterized in that, The protective gas is selected from nitrogen and / or inert gases.

16. The preparation method according to claim 15, characterized in that, The protective gas is selected from at least one of nitrogen, argon and helium.

17. The preparation method according to claim 16, characterized in that, The protective gas is argon.

18. A hydrogen evolution electrode, characterized in that, The hydrogen evolution electrode is obtained by spraying a slurry onto the surface of a gas diffusion layer; the slurry includes the CoZn bimetallic catalyst as described in claim 1.

19. The hydrogen evolution electrode according to claim 18, characterized in that, The gas diffusion layer is made of at least one of carbon paper, nickel foam, and nickel felt.

20. The hydrogen evolution electrode according to claim 18, characterized in that, The slurry also includes anionic polymers and solvents.

21. The hydrogen evolution electrode according to claim 20, characterized in that, In the slurry, the weight ratio of the catalyst to the anionic polymer is (2.33-10):

1.

22. The hydrogen evolution electrode according to claim 20, characterized in that, The solvent is selected from C1-C4 monohydric alcohols.

23. The hydrogen evolution electrode according to claim 22, characterized in that, The solvent is isopropanol.

24. The hydrogen evolution electrode according to claim 18, characterized in that, With the surface area of ​​the hydrogen evolution electrode being 1 cm² 2 The catalyst loading is estimated to be 1-2 mg.

25. The hydrogen evolution electrode according to claim 18, characterized in that, The surface area of ​​the hydrogen evolution electrode is 2-8 cm². 2 .

26. An electrolytic cell, characterized in that, The cathode of the electrolyzer is the hydrogen evolution electrode as described in any one of claims 18-25.

27. The electrolytic cell according to claim 26, characterized in that, The electrolytic cell also includes an oxygen evolution electrode, an anion exchange membrane, and a current collector.

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