CoZn bimetallic catalyst, preparation method thereof, hydrogen evolution electrode and electrolytic bath

Abstract

The invention relates to the field of water electrolysis hydrogen production, and discloses a CoZn bimetallic catalyst, a preparation method thereof, a hydrogen evolution electrode and an electrolytic bath. The X-ray powder diffraction pattern of the catalyst has characteristic peaks when 2 theta is 25.94 + / -0.18 degrees, 44.16 + / -0.18 degrees, 51.44 + / -0.18 degrees and 76.26 + / -0.18 degrees; the content of a Co element in the catalyst is 36.3 to 42.7 wt%, and the content of a Zn element in the catalyst is 0.03 to 5.28 wt%; the average particle size of the catalyst is 90-110 nm. The particle size of the catalyst is proper, so that an electrode material with a stable structure can be prepared, and the electrode material is kept constant and stable under a long-time high-current condition. The catalyst with proper size is combined with a proper catalytic layer structure, so that the prepared hydrogen evolution electrode shows excellent activity and efficiency.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by water electrolysis, and in particular to a CoZn bimetallic catalyst and a preparation method thereof, a hydrogen evolution electrode and an electrolytic cell. Background Art

[0002] In comparison, hydrogen production by water electrolysis uses water as the raw material for electrolysis. During the electrolysis process, hydrogen and oxygen are respectively released at the cathode and anode, and no pollutants are produced. It is a green hydrogen technology.

[0003] The membrane electrode is the core of the membrane electrolyzer, which is crucial to the efficiency and cycle stability of hydrogen production by water electrolysis. In recent years, researchers have invested a lot of energy in the research and development of electrode materials, especially in improving the performance and stability of the catalytic materials themselves and reducing the content of precious metals. However, there are few studies on the transition of electrode materials from the three-electrode system to the electrode structure with good catalytic activity and stability that can be used in the electrolyzer. Facts show that the catalytic electrodes prepared by most catalysts developed in the laboratory cannot show the expected effect and stability. Among them, the particle size of the electrode material spray liquid component has a large correlation with the surface morphology and porosity of the electrode, which in turn affects the performance of hydrogen production by water electrolysis. When the particle size of the catalyst is large, the prepared electrode material is uneven and has poor stability, which makes the electrode surface easy to fall off during the electrolysis process. When the catalyst particle size is small, the electrode material has a relatively uniform surface morphology, but it is easy to form a dense structure, which is not conducive to the contact between the active site and the electrolyte and the rapid desorption of the gas. Therefore, the preparation of catalysts of appropriate size, combined with the appropriate catalytic layer structure, is conducive to obtaining a structurally stable and efficient electrode, which is very critical to the improvement of the performance of the electrolyzer. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of poor stability of the hydrogen evolution electrode in the alkaline membrane electrolyzer system in the prior art, and to provide a CoZn bimetallic catalyst and a preparation method thereof, a hydrogen evolution electrode and an electrolyzer. The catalyst has a suitable particle size, which is conducive to the preparation of a structurally stable electrode material so that it can maintain permanent stability under long-term high current conditions.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a CoZn bimetallic catalyst, wherein the X-ray powder diffraction spectrum 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 element and Zn element in the catalyst are 36.3-42.7wt% and 0.03-5.28wt% respectively; and the average particle size of the catalyst is 90-110nm.

[0006] A second aspect of the present invention provides a method for preparing a CoZn bimetallic catalyst, characterized in that the preparation method comprises 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); based on the total weight of the cobalt source, the zinc source and the nitrogen-containing organic ligand being 1g, the amount of the solvent used is 25-35mL;

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

[0009] The 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 on the surface of a gas diffusion layer; the slurry includes the 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] Through the above technical solution, the beneficial effects of the present invention are:

[0013] By controlling the ratio of cobalt source, zinc source and nitrogen-containing organic ligand, the formed CoZn-ZIF precursor can be heated to obtain a catalyst with appropriate content of Co element, Zn element, N element and C element. By adjusting the solution concentration (amount of solvent) when preparing the precursor, 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 90-110nm. The size of the catalyst formed by heating the precursor is 90-110nm, and the size of the formed catalyst is suitable. The catalyst is prepared into a slurry as an active component, and the amount of each component of the electrode spray slurry is selected, and it is sprayed on the surface of the gas diffusion layer to obtain an efficient and stable hydrogen evolution electrode for hydrogen evolution reaction, which improves the overall efficiency and stability of hydrogen production by alkaline membrane water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a SEM image of the CoZn-ZIF precursor prepared in Example 1 of the present invention;

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

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

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

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

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

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

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

[0022] Fig. 9 It is a SEM picture of the CoZn-ZIF precursor prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The first aspect of the present invention provides a CoZn bimetallic catalyst, wherein the X-ray powder diffraction spectrum 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 element and Zn element in the catalyst are 36.3-42.7wt% and 0.03-5.28wt% respectively; and the average particle size of the catalyst is 90-110nm.

[0025] The X-ray powder diffraction spectrum of the CoZn bimetallic catalyst of the present invention has a diffraction peak of the carbon component in the structure at 2θ of 25.94±0.18°, and a characteristic peak of CoN in the structure 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 content of the Zn element in the catalyst is small, and the crystallinity of the material is general, so the structure corresponding to the obvious Zn element is not measured. The average particle size of the bimetallic catalyst material is 90-110nm, and the particle size is suitable, which is conducive to the preparation of a structurally stable electrode material, so that it can maintain permanent stability under long-term high current conditions. The catalyst of suitable size is combined with an appropriate catalyst layer structure, so that the prepared hydrogen evolution electrode exhibits excellent activity and efficiency. In addition, a large number of carbon nanotube structures are generated on the catalyst surface, and the carbon nanotube structure can increase the specific surface area of ​​the material, reduce resistance, and enhance the catalytic stability of the material.

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

[0027] In order to further improve the activity and efficiency of the prepared hydrogen evolution electrode, preferably, the average particle size of the catalyst is 97-103 nm.

[0028] A second aspect of the present invention provides a method for preparing a CoZn bimetallic catalyst, characterized in that the preparation method comprises 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); based on the total weight of the cobalt source, the zinc source and the nitrogen-containing organic ligand being 1g, the amount of the solvent used is 25-35mL;

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

[0031] The present invention uses cobalt element and zinc element as framework nodes, coordinates with nitrogen-containing organic ligands, obtains CoZn bimetallic zeolite imidazolate framework precursor (CoZn-ZIF precursor), heats it (annealing) in the presence of protective gas, nitrogen-containing organic ligands are carbonized, and C / N doping exists in the formed CoZn bimetallic catalyst, Co and Zn both exist in the form of metal, and are connected to each other through C, N components in the structure, and the C / N-doped CoZn bimetallic catalyst of surface-loaded carbon nanotubes is obtained. By controlling the ratio of cobalt source, zinc source and nitrogen-containing organic ligands, the formed CoZn-ZIF precursor can be heated to obtain a catalyst with suitable content of Co element, Zn element, N element and C element. By adjusting the solution concentration (consumption of solvent) when preparing the precursor, and the ratio of cobalt source, zinc source and nitrogen-containing organic ligands, the size of the CoZn-ZIF precursor is maintained at 90-110nm. The precursor is heated, and the nitrogen-containing organic ligands therein are carbonized to form a catalyst with a size of 90-110nm. The catalyst is of suitable size, and the catalyst is used as an active component to prepare a slurry, which is sprayed on the surface of a gas diffusion layer to obtain an efficient and stable hydrogen evolution electrode.

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

[0033] According to the present invention, preferably, the zinc source is selected from water-soluble zinc salts, preferably at least one selected from zinc chloride and zinc nitrate, 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, preferably 2-methylimidazole.

[0035] The present invention has no particular requirements on the type of solvent used when the cobalt source, zinc source and nitrogen-containing organic ligand react, as long as the reaction of the cobalt source, zinc source and nitrogen-containing organic ligand can proceed smoothly. Preferably, the solvent is selected from C1-C4 monohydric alcohol, preferably methanol.

[0036] The use of 2-methylimidazole as the nitrogen-containing organic ligand can simplify the preparation process of the catalyst, and a CoZn-ZIF precursor with regular morphology can be synthesized at room temperature. Preferably, the reaction temperature is 20-30° C. and the reaction time is 20-30 hours.

[0037] In order to make the cobalt source, the zinc source and the 2-methylimidazole mix more evenly, so as to facilitate the smooth progress of the reaction, preferably, the preparation method of the CoZn-ZIF precursor comprises the following steps:

[0038] S1, mixing the cobalt source, the zinc source and the solvent for the first time to obtain a mixed solution A;

[0039] S2, mixing 2-methylimidazole and the solvent for a second time to obtain a mixed solution B;

[0040] S3, performing a third mixing of the mixed solution A and the mixed solution B and performing the reaction to obtain the precursor.

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

[0042] In order to make the cobalt source, zinc source and 2-methylimidazole mix more evenly, so as to facilitate the smooth progress of the reaction, preferably, based on the total amount of the cobalt source and zinc source as 1g, the amount of the solvent in S1 is 35-50mL; based on the amount of 2-methylimidazole as 1g, the amount of the solvent in S2 is 18-25mL.

[0043] In order to obtain a pure precursor, S3 further includes: after the reaction, washing and drying the solid phase product to obtain the precursor. A solvent that does not destroy the catalyst morphology and structure and is easily volatile is selected for washing, for example, anhydrous ethanol can be used for washing.

[0044] In the present invention, the cobalt source and the zinc source may exist in a form containing or not containing bound water, the cobalt nitrate may be Co(NO3)2·6H2O, and the zinc nitrate may be Zn(NO3)2·6H2O. When selecting the amount of solvent, the cobalt nitrate and zinc nitrate are measured in the form of Co(NO3)2·6H2O and Zn(NO3)2·6H2O, respectively.

[0045] According to the above conditions, a CoZn-ZIF precursor with uniform particle size (average particle size of 90-110 nm) and regular morphology can be obtained.

[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 1.5-2.5h.

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

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

[0049] The 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 on the surface of a gas diffusion layer; the slurry includes the CoZn bimetallic catalyst provided by the present invention.

[0051] The gas diffusion layer is an important basic material for manufacturing membrane electrodes. When the battery performs an electrochemical reaction, the gas diffusion layer not only provides a transmission channel for gas phase reactants and liquid water, but also provides a conduction channel for electricity and heat. The present invention has no special requirements on the material of the gas diffusion layer, and the conventional gas diffusion layer for preparing membrane electrodes in the art 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 comprises an anionic polymer and a solvent.

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

[0054] In order to further improve the surface morphology and pore size of the prepared membrane electrode material, so that the hydrogen evolution electrode exhibits excellent hydrogen evolution performance and lasting stability in hydrogen production in an alkaline membrane electrolyzer, preferably, the concentration of the anionic polymer in the slurry is 1-4.29 mg / mL.

[0055] The average particle size of the CoZn bimetallic catalyst of the present invention is 90-110nm, which is suitable for preparing electrode materials with stable structure, so that it can maintain long-term stability under long-term high current conditions. Then, by selecting the amount of each component of the electrode spray slurry, an efficient and stable gas diffusion electrode is obtained for hydrogen evolution reaction, which improves the overall efficiency and stability of hydrogen production by alkaline membrane water electrolysis.

[0056] The present invention has no particular restrictions on the type of anionic polymer, and can be an anionic polymer conventionally used for membrane electrodes in the art. The present invention has no particular restrictions on the weight average molecular weight of the anionic polymer, as long as it can meet the requirements for membrane electrodes. For example, the anionic polymer can be selected from 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 the present invention, the amount of the anionic polymer is calculated in the form of no solvent.

[0058] The present invention has no particular requirements on the type of solvent used in the slurry, and it can be a conventional solvent for preparing a spray slurry for a hydrogen evolution electrode in the art. Preferably, the solvent is selected from C1-C4 monohydric alcohols, more preferably isopropanol.

[0059] According to the present invention, preferably, the surface area of ​​the hydrogen evolution electrode is 1 cm 2 The loading amount of the catalyst is 1-2 mg. When the loading amount meets this range, the active area of ​​the catalyst can be effectively utilized. Otherwise, when the loading amount is small, the active area of ​​the catalyst is reduced; when the loading amount is too high, the active area of ​​the catalyst remains basically unchanged, but the electron conduction is blocked, thereby affecting the catalytic performance.

[0060] According to the present invention, preferably, the surface area of ​​the hydrogen evolution electrode is 2-8 cm 2 The surface area of ​​the hydrogen evolution electrode meets this range, which is conducive to the rapid overflow of the generated gas and the increase of 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 comprises an oxygen evolution electrode, an anion exchange membrane (AEM) and a current collector.

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

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

[0065] The electrolytic cell includes two current collectors. The present invention has no particular limitation on the material of the current collectors, which may 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. In the following examples, unless otherwise specified, all conventional methods are used; the reagents and materials used, unless otherwise specified, can be obtained from commercial sources. The materials and test methods involved in each example and comparative example are as follows:

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

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

[0069] The electrochemical performance test was carried out using an IPS 100A electrochemical workstation.

[0070] The following examples are used to illustrate the preparation of catalysts and hydrogen evolution electrodes.

[0071] Example 1

[0072] S1. Weigh cobalt nitrate and zinc nitrate in a beaker, then add methanol (the total amount of cobalt nitrate and zinc nitrate is 1g, and the amount of methanol is 41.6mL), stir to dissolve it, and obtain 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 a methanol solution (the amount of 2-methylimidazole is 1g, and the amount of methanol is 23mL), and stir to obtain solution B. Subsequently, under stirring, solution B is added to solution A to mix it evenly. The above solution is stirred at 25°C for 24h, centrifuged, and the product is washed three times with anhydrous ethanol to obtain a CoZn-ZIF precursor material, which is dried for standby use.

[0073] S2. Weigh 2g of dry CoZn-ZIF precursor material in the middle of a vertical furnace. Pass argon at a flow rate of 30mL / min for 2h to fully remove the remaining gases in the system; then adjust the argon flow rate to 20mL / min, and slowly heat to 700℃ at a heating rate of 5℃ / min under the condition of continuous argon flow, and keep at this temperature for 2h, and naturally cool 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, prepare the catalyst into a spray ink, the spray ink solvent is isopropanol, add anionic polymer A5-HCO3, the contents of catalyst and A5-HCO3 (the amount of A5-HCO3 is calculated as solute) in the spray ink are 10mg / mL and 2.5mg / mL respectively, and the prepared solution is ultrasonically dispersed for 1h. Spray the spray ink onto the surface of the gas diffusion layer (Toray carbon paper 060, thickness 0.19mm) by spraying to obtain a hydrogen evolution electrode. The electrode area is 4cm 2 , the catalyst loading was 2 mg cm -2 .

[0075] Example 2

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

[0077] Example 3

[0078] A hydrogen evolution electrode was prepared according to the method of 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 was 4.29 mg / mL" was used to replace "the content of A5-HCO3 in the spray ink was 2.5 mg / mL". A hydrogen evolution electrode was obtained.

[0079] Example 4

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

[0081] Example 5

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

[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, "nickel foam with a thickness of 0.2 mm and a catalyst loading of 1 mg cm -2 "Replace" Toray carbon paper 060; catalyst loading is 2 mg cm -2 ". A hydrogen evolution electrode was obtained.

[0085] Example 7

[0086] A hydrogen evolution electrode was prepared according to the method of 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; the content of A5-HCO3 in the spray ink was 2.5 mg / mL" was replaced by "foam nickel with a thickness of 0.2 mm; the content of A5-HCO3 in the spray ink was 4.29 mg / mL". A hydrogen evolution electrode was prepared.

[0087] Example 8

[0088] A hydrogen evolution electrode was prepared according to the method of Example 1, except that the type of the gas diffusion layer was different. Specifically, in S3, "Toray carbon paper 060" was replaced with "nickel felt with a thickness of 0.25 mm". A hydrogen evolution electrode was prepared.

[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 and a catalyst loading of 1 mg cm -2 "Replace" Toray carbon paper 060; catalyst loading is 2 mg cm -2 ". A hydrogen evolution electrode was obtained.

[0091] Example 10

[0092] A hydrogen evolution electrode was prepared according to the method of 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; the content of A5-HCO3 in the spray ink was 2.5 mg / mL" was replaced by "nickel felt with a thickness of 0.25 mm; the content of A5-HCO3 in the spray ink was 1 mg / mL". A hydrogen evolution electrode was prepared.

[0093] Embodiment 11

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

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

[0096] Example 12

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

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

[0099] Example 13

[0100] A hydrogen evolution electrode was prepared according to the method of 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 was 0.53 mg / mL" was used to replace "the content of A5-HCO3 in the spray ink was 2.5 mg / mL". A hydrogen evolution electrode was obtained.

[0101] Embodiment 14

[0102] A hydrogen evolution electrode was prepared according to the method of 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 was 6.67 mg / mL" was used to replace "the content of A5-HCO3 in the spray ink was 2.5 mg / mL". A hydrogen evolution electrode was obtained.

[0103] Embodiment 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 cm -2 The catalyst loading of "replacement" was 2 mg cm -2 ". A hydrogen evolution electrode was obtained.

[0105] Comparative Example 1

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

[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] A hydrogen evolution electrode was prepared according to the method of Example 1, except that in S1, "based on the total amount of cobalt nitrate and zinc nitrate being 1 g, the amount of methanol being 13.9 mL; based on the amount of 2-methylimidazole being 1 g, the amount of methanol being 7.6 mL" was used to replace "based on the total amount of cobalt nitrate and zinc nitrate being 1 g, the amount of methanol being 41.6 mL; based on the amount of 2-methylimidazole being 1 g, the amount of methanol being 23 mL". A CoZn-ZIF precursor material was obtained, and then a catalyst was obtained, and then a hydrogen evolution electrode was obtained.

[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] A hydrogen evolution electrode was prepared according to the method of Example 1, except that "the weight ratio of cobalt nitrate, zinc nitrate and 2-methylimidazole is 2:1:5.5" was replaced by "the weight ratio of cobalt nitrate, zinc nitrate and 2-methylimidazole is 2:1:2.73". A CoZn-ZIF precursor material was obtained, and then a catalyst was obtained, and then a hydrogen evolution electrode was obtained.

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

[0114] Test Example 1

[0115] The Co-ZIF precursor material, Co-based catalyst and hydrogen evolution electrode were detected by scanning electron microscopy; and the X-ray powder diffraction pattern of the Co-based catalyst was measured by X-ray diffractometer.

[0116] The scanning electron microscope image of the CoZn-ZIF precursor prepared in Example 1 is as follows: Figure 1 As shown by Figure 1It can be seen that the average particle size of the CoZn-ZIF precursor is 100 nm. Figure 1 Similarly, the average particle size is in the range of 90-110 nm, which is not shown in the text. The scanning electron microscopy images of the CoZn-ZIF precursors prepared in Comparative Examples 1, 2 and 3 are shown in FIG. Figure 7 , Figure 8 and Fig. 9 As shown by Figure 7 , Figure 8 and Fig. 9 It can be seen that the average particle sizes of the CoZn-ZIF precursor particles obtained in Comparative Examples 1, 2 and 3 are 500 nm, 1 μm and 110 nm respectively. The particle integrity of the CoZn-ZIF precursor obtained in Comparative Example 3 is poor and the particle size is uneven.

[0117] The average particle size of the catalyst prepared in Example 1 was measured by scanning electron microscopy to be 102 nm. The average particle sizes of the catalysts prepared in Examples 11 and 12 were 110 nm and 100 nm (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 (not shown in the text).

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

[0119] The X-ray powder diffraction spectrum of the catalyst prepared in Example 1 is as follows: Figure 3 As shown by Figure 3 It can be seen that the X-ray powder diffraction peak position of the catalyst is expressed in 2θ angles, with the diffraction peak of the carbon component in the structure at 25.94°, and the characteristic peaks of CoN in the structure at 44.16°, 51.44° and 76.26°, indicating that the catalyst is a C / N-doped CoZn bimetallic material. Figure 1 Similarly, not shown in the text.

[0120] The scanning electron microscope image of the hydrogen evolution electrode prepared in Example 1 of the present invention is as follows: 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 examples and comparative examples were used in alkaline membrane electrolyzers. The effective area of ​​the single cell was 4 cm 2, which consists of an oxygen evolution electrode, a hydrogen evolution electrode, an anion exchange membrane (AEM membrane, brand PiperION, thickness 40μm) and two stainless steel current collectors. The AEM membrane was immersed in a 1mol / L KOH solution at room temperature for 24h, the alkali solution on the surface was rinsed off with deionized water, and then placed between the oxygen evolution electrode and the hydrogen evolution electrode. The stainless steel clamps on both sides of the electrode were clamped with a force of 4Nm, and the electrodes were sealed with a polytetrafluoroethylene gasket of appropriate thickness. After the electrodes were installed, a constant current method (10mA cm -2 , 5min; 20mAcm -2 , 5min; 30mA cm -2 , 5min; 40mA cm -2 , 5min; 50mA cm -2 , 5min; 100mA cm -2 , 5min; 200mA cm -2 , 5min; 300mA cm -2 , 5min; 400mA cm -2 , 5min; 500mA cm -2 , 5 min) for activation, and then the polarization curve of the electrode was tested, as well as the 500 mA cm -2 The durability of the alkaline exchange membrane water electrolyzer (AEMWE) was evaluated at a current density of 500 mA / cm. The AEMWE was tested at 60°C with 1 mol / L KOH as the electrolyte (flow rate 4-8 mL / min). 2 The cell voltage and current density are 500mA / cm 2 The average electrode decay rate results within 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 Embodiment 11 1.912 1.175 Example 12 1.895 0.874 Example 13 1.868 0.927 Embodiment 14 1.882 0.923 Embodiment 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. 2 The cell voltage is 1.845V and the current density is 1A / cm 2 The cell voltage is 1.969V.

[0126] The electrode stability curve obtained in Example 1 is as follows Figure 6 As shown by Figure 6 It can be seen that at a current density of 500 mA / cm 2It showed very good stability in the 100-hour stability test. The average decay rate within 100 hours was 0.821mV / h.

[0127] The results in Table 1 show that the hydrogen evolution electrodes prepared by the CoZn bimetallic catalysts of Examples 1-15 have a current density of 500 mA / cm 2 The average electrode decay rate within 100 hours is below 1.175 mV / h; Comparative Example 1 changes the ratio and concentration of the cobalt source, zinc source and nitrogen-containing organic ligand when preparing the precursor, and Comparative Example 2 changes the concentration of the cobalt source, zinc source and nitrogen-containing organic ligand when preparing the precursor; Comparative Example 3 changes the ratio of the cobalt source, zinc source and nitrogen-containing organic ligand when preparing the precursor. Compared with Examples 1-15, the average electrode decay rate increases, which shows that the catalyst of the present invention can obtain a high-efficiency electrode with stable structure.

[0128] In addition, in Example 5 and Example 8, carbon paper is replaced by nickel foam and nickel felt, respectively. Compared with Example 1, the average decay rate of the hydrogen evolution electrode obtained in Example 5 and Example 8 is increased; the difference between Example 10 and Example 2 is that in Example 10, carbon paper is replaced by nickel felt. Compared with Example 2, the average decay rate of the hydrogen evolution electrode obtained in Example 10 is increased, which shows that the selection of the preferred gas diffusion layer can further improve the stability of the hydrogen evolution electrode. In Example 11 and Example 12, the calcination temperature of the precursor is changed. Compared with Example 1, the average decay rate of the hydrogen evolution electrode obtained in Example 11 and Example 12 is increased, which shows that the stability of the hydrogen evolution electrode can be further improved when the calcination temperature of the precursor meets the preferred conditions. In Example 13 and Example 14, the weight ratio of the catalyst and the anionic polymer in the spray slurry is changed, respectively. Compared with Example 1, the average decay rate of the hydrogen evolution electrode obtained in Example 13 and Example 14 is increased, which shows that the stability of the hydrogen evolution electrode can be further improved when the weight ratio of the catalyst and the anionic polymer in the spray slurry meets the preferred conditions. Example 15 increases the loading amount of the catalyst on the hydrogen evolution electrode. Compared with Example 1, the average decay rate of the hydrogen evolution electrode prepared in Example 15 increases. This indicates that when the loading amount of the catalyst on the hydrogen evolution electrode meets the preferred conditions, the stability of the hydrogen evolution electrode can be further improved.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A CoZn bimetallic catalyst, characterized in that: The X-ray powder diffraction spectrum 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 element and Zn element in the catalyst are 36.3-42.7wt% and 0.03-5.28wt% respectively; and the average particle size of the catalyst is 90-110nm.

2. The CoZn bimetallic catalyst according to claim 1, characterized in that The content of N element in the catalyst is 3.55-3.72wt%; and / or, the content of C element in the catalyst is 50.8-59.5wt%; Preferably, the average particle size of the catalyst is 97-103 nm.

3. A method for preparing a CoZn bimetallic catalyst, characterized in that: The preparation method comprises 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); based on the total weight of the cobalt source, the zinc source and the nitrogen-containing organic ligand being 1g, the amount of the solvent used is 25-35mL; S2. In the presence of a protective gas, the precursor is heated to obtain a CoZn bimetallic catalyst.

4. The preparation method according to claim 3, characterized in that: The cobalt source is selected from water-soluble cobalt salts, preferably cobalt chloride and / or cobalt nitrate, more preferably cobalt nitrate; Preferably, the zinc source is selected from water-soluble zinc salts, preferably at least one selected from zinc chloride and zinc nitrate, more preferably zinc nitrate; Preferably, the nitrogen-containing organic ligand is selected from imidazole and / or 2-methylimidazole, preferably 2-methylimidazole; Preferably, the solvent is selected from C1-C4 monohydric alcohols, preferably methanol; Preferably, the reaction temperature is 20-30°C and the reaction time is 20-30h.

5. The preparation method according to claim 3 or 4, characterized in that: 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 1.5-2.5h; Preferably, the protective gas is selected from nitrogen and / or an inert gas, preferably selected from at least one of nitrogen, argon and helium, more preferably argon.

6. A CoZn bimetallic catalyst prepared by the preparation method according to any one of claims 3 to 5.

7. A hydrogen evolution electrode, characterized in that The hydrogen evolution electrode is obtained by spraying a slurry on the surface of a gas diffusion layer; the slurry comprises the CoZn bimetallic catalyst according to any one of claims 1, 2, and 5; Preferably, the material of the gas diffusion layer is selected from at least one of carbon paper, nickel foam and nickel felt.

8. The hydrogen evolution electrode according to claim 7, characterized in that The slurry also includes an anionic polymer and a solvent; Preferably, in the slurry, the weight ratio of the catalyst to the anionic polymer is (2.33-10):1; Preferably, the solvent is selected from C1-C4 monohydric alcohols, preferably isopropanol.

9. The hydrogen evolution electrode according to claim 7 or 8, characterized in that The surface area of ​​the hydrogen evolution electrode is 1 cm 2 The catalyst loading is 1-2 mg; Preferably, the surface area of ​​the hydrogen evolution electrode is 2-8 cm 2 .

10. An electrolytic cell, characterized in that: The cathode of the electrolytic cell is the hydrogen evolution electrode according to any one of claims 7 to 9; Preferably, the electrolytic cell further comprises an oxygen evolution electrode, an anion exchange membrane and a current collector.

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