Surface modification method of transition metal-based water electrolysis catalytic material and catalytic material

Abstract

The surface modification method of the transition metal-based water electrolysis catalytic material and the catalytic material are disclosed. The surface modification method comprises: taking the transition metal-based water electrolysis catalytic material to be modified as a target substrate; immersing the target substrate into a first solution for etching treatment to form an etching morphology on the surface of the target substrate; immersing the target substrate after the etching treatment into a second solution for modification treatment to grow layered double hydroxide nanoarrays on the surface of the target substrate, and to obtain the modified transition metal-based water electrolysis catalytic material. According to the embodiments of the present disclosure, more active sites can be exposed on the surface of the existing transition metal-based water electrolysis catalytic material, and then the electronic structure of the active sites can be regulated through high-valence metals, so as to improve the electrocatalytic water splitting performance.

Description

Technical Field

[0001] This disclosure relates to the field of water electrolysis catalytic materials technology, and in particular to a surface modification method for a transition metal-based water electrolysis catalytic material and the water electrolysis catalytic material itself. Background Technology

[0002] In order to minimize energy loss in the energy conversion process, it is urgent to develop efficient and superior catalytic materials to promote the oxygen evolution reaction in water electrolysis, reduce the anode overpotential, and thus reduce the overall energy consumption of the alkaline electrolyzer.

[0003] Currently, non-precious metals such as nickel, iron, and titanium are widely used as catalytic materials in commercial alkaline electrolyzers due to their excellent hydrogen and oxygen evolution activity and resistance to impurities during water electrolysis. However, because nickel-based, iron-based, and titanium-based water electrolysis catalytic materials have a relatively small number of surface active sites during the reaction process, they require a large overpotential under industrial high current densities, resulting in high energy consumption for water electrolysis that is difficult to meet the needs of commercial production. This significantly reduces the utilization efficiency of nickel, iron, and titanium-based materials, thus hindering their further development in practical industry. Therefore, how to develop highly active, low-cost, and long-term stable electrocatalytic materials under industrial-grade high current conditions remains an urgent problem to be solved. Summary of the Invention

[0004] In view of this, the present disclosure provides a surface modification method for a transition metal-based water electrolysis catalyst and a water electrolysis catalyst, which can expose more active sites on the surface of existing transition metal-based water electrolysis catalysts, thereby reducing the anode overpotential, reducing reaction energy consumption, and meeting the requirements for use under industrial-grade high current conditions.

[0005] In a first aspect, embodiments of this disclosure provide a method for surface modification of a transition metal-based water electrolysis catalyst, the surface modification method comprising:

[0006] The transition metal-based water electrolysis catalyst to be modified was used as the target substrate;

[0007] The target substrate is immersed in the first solution for etching, forming an etched morphology on the surface of the target substrate;

[0008] The etched target substrate was immersed in a second solution for modification, and a layered double hydroxide nanoarray was grown on the surface of the target substrate to obtain a modified transition metal-based water electrolysis catalyst.

[0009] Optionally, the metal-based water electrolysis catalyst includes any one of the following catalysts: nickel-based catalysts, iron-based catalysts, cobalt-based catalysts, and titanium-based catalysts.

[0010] Optionally, the first solution is a mixed solution of nitric acid, sodium hypochlorite solution and water, wherein the volume ratio of nitric acid, sodium hypochlorite solution and water is 1:1:10 to 1:1:20.

[0011] Optionally, the second solution contains one or more metal cations that are different from the target substrate, such as iron ions, manganese ions, cobalt ions, molybdenum ions, and chromium ions.

[0012] Optionally, the concentration of any one of the metal cations in the second solution is 50 μmol / ml to 100 μmol / ml.

[0013] Optionally, the second solution contains metatungstate ions.

[0014] Optionally, the second solution is a mixed solution of ammonium metatungstate and nitrate, wherein the molar ratio of ammonium metatungstate to nitrate is 1:2 to 1:15.

[0015] Optionally, a surfactant is added to the second solution, and the ratio between the sum of the amounts of ammonium metatungstate and nitrate and the amount of surfactant is 8:1 to 1:2.

[0016] Optionally, the surfactant may include one of sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and hexadecyltrimethylammonium bromide (CTAB).

[0017] Secondly, embodiments of this disclosure provide a water electrolysis catalytic material, including a transition metal-based water electrolysis catalytic material and a layered double hydroxide nanoarray modified on the surface of the transition metal-based water electrolysis catalytic material. The water electrolysis catalytic material is prepared by the surface modification method of the transition metal-based water electrolysis catalytic material described above.

[0018] As described above, this disclosure provides a method for surface modification of transition metal-based water electrolysis catalysts. The method includes: first, using the transition metal-based water electrolysis catalyst to be modified as a target substrate; then, immersing the target substrate in a first solution for etching treatment to form an etched morphology on the surface of the target substrate; finally, immersing the etched target substrate in a second solution for modification treatment to grow a layered double hydroxide nanoarray on the surface of the target substrate. Because the modified transition metal-based water electrolysis catalyst has a layered double hydroxide nanoarray on its surface, compared to the smooth surface of existing transition metal-based water electrolysis catalysts, its specific surface area is increased, enhancing the exposure of its surface active sites. This facilitates sufficient contact of the electrolyte and rapid charge migration during the heterogeneous catalytic process of water electrolysis, thereby reducing the anodic overpotential, reducing reaction energy consumption, and meeting the requirements for use under industrial-grade high-current conditions.

[0019] The above description is merely an overview of the technical solution disclosed herein. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 Scanning electron microscope image of untreated pure foamed nickel catalyst provided in the embodiments of this disclosure;

[0022] Figure 2 A flowchart illustrating the surface modification method for transition metal-based water electrolysis catalysts provided in this disclosure embodiment;

[0023] Figure 3 Scanning electron microscope images of acid-etched pure foamed nickel catalyst materials provided in embodiments of this disclosure;

[0024] Figure 4 Scanning electron microscope image of pure nickel foam catalyst material modified with layered double hydroxide nanoarray provided in the embodiments of this disclosure;

[0025] Figure 5 Scanning electron microscope image of pure nickel foam catalyst material modified with layered double hydroxide nanoarray containing high-valence ions, provided in the embodiments of this disclosure;

[0026] Figure 6 X-ray photoelectron spectroscopy of the pure nickel foam catalyst modified with a layered double hydroxide nanoarray containing high-valence ions, as provided in the embodiments of this disclosure. Figure 1 ;

[0027] Figure 7 X-ray photoelectron spectroscopy of the pure nickel foam catalyst modified with a layered double hydroxide nanoarray containing high-valence ions, as provided in the embodiments of this disclosure. Figure 2 ;

[0028] Figure 8 Linear scan voltammetric curves of pure nickel foam catalysts etched and modified at different scales according to embodiments of this disclosure;

[0029] Figure 9 The constant current stability test diagrams of pure nickel foam catalysts etched and modified at different scales according to the embodiments of this disclosure are shown. Detailed Implementation

[0030] The present disclosure will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present disclosure are shown in the accompanying drawings.

[0031] It should be noted that, where there is no conflict, the embodiments and features described in this disclosure can be combined with each other. The technical solutions of this disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] Unless otherwise stated, the exemplary implementations / embodiments shown are to be understood as providing exemplary features of various details that provide ways in which the technical concepts of this disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of various implementations / embodiments may be additionally combined, separated, interchanged and / or rearranged without departing from the technical concepts of this disclosure.

[0033] The use of crosshairs and / or shading in the accompanying drawings is generally used to clarify the boundaries between adjacent components. Thus, unless otherwise stated, the presence or absence of crosshairs or shading does not convey or indicate any preference or requirement for the specific material, material properties, dimensions, proportions, commonalities between the illustrated components, or any other characteristics, properties, etc., of the components. Furthermore, in the accompanying drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than that described. For example, two consecutively described processes may be performed substantially simultaneously or in the reverse order of their description. Furthermore, the same reference numerals denote the same components.

[0034] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof. It should also be noted that, as used herein, the terms “substantially,” “about,” and other similar terms are used as approximate terms rather than as terms of degree, thus explaining the inherent biases in measurements, calculated values, and / or provided values ​​that would be recognized by one of ordinary skill in the art.

[0035] Currently, the water electrolysis catalysts widely used in commercial alkaline electrolyzers are non-precious metal-based catalysts such as nickel-based, iron-based, and titanium-based catalysts. Commercial alkaline electrolyzers typically operate at high current densities. Taking nickel-based water electrolysis catalysts as an example, these include nickel plates, nickel meshes, and nickel foam. These catalysts require large overpotentials under high industrial current densities, which hinders their further development in practical industrial applications.

[0036] Existing non-precious metal-based catalytic materials, such as nickel-based, iron-based, and titanium-based catalytic materials, have relatively smooth surfaces. Figure 1 The surface morphology of pure nickel foam catalyst is shown in the figure. It can be seen that pure nickel foam catalyst has a smooth surface, a small specific surface area, is difficult to adsorb water, and has poor electrocatalytic hydrolysis performance.

[0037] The inventors considered modifying its surface to provide more active sites and a better electronic coordination environment, reduce the reaction overpotential, thereby reducing reaction energy consumption, improving its catalytic performance, and meeting its application requirements under industrial-grade high-current conditions. This led to the development of a highly active, low-cost, and long-term stable water electrolysis catalytic material suitable for industrial-grade high-current conditions.

[0038] Based on this, this disclosure provides a surface modification method for transition metal-based water electrolysis catalysts to modify the surface of existing commercial nickel-based, iron-based, and titanium-based catalysts. Existing commercial metal-based water electrolysis catalysts all belong to the transition metal series. Compared with noble metal-based water electrolysis catalysts, transition metal-based water electrolysis catalysts have the advantages of moderate price and good catalytic performance, and are commonly used in commercial alkaline electrolyzers.

[0039] See Figure 2 The surface modification method for transition metal-based water electrolysis catalysts provided in this disclosure includes steps S1 to S3.

[0040] S1. The transition metal-based water electrolysis catalyst to be modified is used as the target substrate.

[0041] For example, the transition metal-based water electrolysis catalyst to be modified includes any one of the following catalysts: nickel-based catalysts, iron-based catalysts, cobalt-based catalysts, and titanium-based catalysts. Specifically, nickel-based catalysts may include nickel plates, nickel meshes, and nickel foam; iron-based catalysts may include iron plates, iron meshes, and iron foam; titanium-based catalysts may include titanium plates, titanium meshes, and titanium foam; and cobalt-based catalysts may include cobalt plates, cobalt meshes, and cobalt foam.

[0042] In practice, the modified metal-based water electrolysis catalyst material can be pretreated to clean impurities such as dust, organic matter and inorganic matter from its surface.

[0043] For example, a 10cm×10cm nickel-based catalyst can be placed in acetone, ethanol and deionized water in sequence and ultrasonically treated for 10min~25min, then placed in a drying oven and dried at a constant temperature of 40℃~60℃ for later use.

[0044] S2. Immerse the target substrate in the first solution for etching treatment to form an etched morphology on the surface of the target substrate.

[0045] For example, the first solution may be an acidic solution.

[0046] Specifically, the first solution can be a mixture of nitric acid, sodium hypochlorite solution, and water. The sodium hypochlorite solution is obtained by absorbing chlorine gas with sodium hydroxide, and contains a large amount of chloride and hypochlorite ions. It should be noted that both the nitric acid and sodium hypochlorite solution can be industrial standard products and do not require additional preparation.

[0047] Taking nickel foam as an example, the etching process in step S2 can be understood as follows:

[0048] During the impregnation of nickel foam in a mixed solution of nitric acid, sodium hypochlorite, and water, the vigorous oxidation reaction of chloride ions, the vigorous reduction reaction of hypochlorite ions, and the strong oxidizing property of nitrate ions in the solution will etch the surface of the nickel foam, forming a micron-scale etched morphology, which provides a good active substrate for the modification and growth of nickel-based nanoarrays.

[0049] Figure 3 The etching morphology of the nickel foam surface is shown in the figure. It can be seen that the nickel foam surface was etched with mixed acid to form pits ranging from 2μm to 10μm. Figure 3 The diameters of the four pores shown are 2.65 μm, 2.20 μm, 3.17 μm and 2.47 μm, respectively; and the etching along the grain boundary increases the specific surface area of ​​the nickel foam, enhances the exposure of the active sites on the surface of the nickel foam, and helps the electrolyte to have sufficient contact and rapid charge migration during the heterogeneous catalysis process of water electrolysis.

[0050] For example, the volume ratio of nitric acid, sodium hypochlorite solution, and water can be 1:1:10 to 1:1:20. Within this volume ratio range, the concentrations of chloride ions, hypochlorite ions, and nitrate ions are moderate, which can form a more ideal etching morphology on the surface of nickel foam, thereby providing a good active substrate for the growth of nanoarray structures. Conversely, excessively high or low concentrations of chloride ions, hypochlorite ions, and nitrate ions will inhibit the etching reaction.

[0051] In practice, the pretreated nickel-based catalyst material can be immersed in a mixed solution at room temperature for 3 to 8 minutes in a volume ratio of nitric acid and sodium hypochlorite solution of 1:1, or in a volume ratio of the sum of the volumes of nitric acid and sodium hypochlorite solution to water of 1:5 to 1:10. After immersion, the material is rinsed several times with deionized water and placed in a drying oven at 30°C to 70°C for 8 to 16 hours to obtain a micron-sized etchable nickel-based catalyst material.

[0052] For example, the nickel foam is immersed in a mixed solution of nitric acid, sodium hypochlorite, and water for 3 to 8 minutes. Within this time range, the etching time of chloride ions, hypochlorite ions, and nitrate ions is moderate, which can form a relatively ideal etching morphology on the nickel foam surface, thereby providing a good active substrate for the growth of nanoarray structures. Conversely, if the etching time of chloride ions, hypochlorite ions, and nitrate ions is too high or too low, it will lead to the dissolution of nickel foam or insufficient etching depth.

[0053] S3. The etched target substrate is immersed in the second solution for modification treatment, and a layered double hydroxide nanoarray is grown on the surface of the target substrate to obtain the modified transition metal-based water electrolysis catalyst.

[0054] The second solution contains one or more metal cations that are different from the target substrate, namely: iron ions, manganese ions, cobalt ions, molybdenum ions, and chromium ions. Taking a nickel-based catalyst as an example, the second solution may contain one or more of the following metal cations other than nickel: iron ions, manganese ions, chromium ions, and cobalt ions.

[0055] For example, the second solution can be a salt solution. The anion in the second solution can be nitrate ions. Specifically, the second solution can be a mixture of one or two nitrates selected from ferric nitrate, manganese nitrate, cobalt nitrate, molybdenum nitrate, and chromium nitrate, and water.

[0056] Taking ferric nitrate as an example, the modification treatment in step S3 can be understood as:

[0057] During the immersion process of etched nickel foam in ferric nitrate solution, the active nickel ions on the surface of the nickel foam grow into NiFe-LDH nanoarrays under the action of iron ions and water in the solution. The NiFe-LDH nanoarrays are binary layered double hydroxide nanoarrays of nickel and iron, which can provide more active sites and excellent electronic coordination environment.

[0058] Figure 4The image shows the surface morphology of NiFe-LDH nanoarray-modified nickel foam. It can be seen that the surface of the nickel foam is modified with a uniformly distributed NiFe-LDH layered double hydroxide nanoarray structure, which increases the specific surface area, enhances the exposure of active sites on the nickel foam surface, and facilitates sufficient electrolyte contact and rapid charge migration during heterogeneous water electrolysis catalysis. Compared with the smooth surface of existing nickel foam, nickel foam modified with NiFe-LDH layered double hydroxide nanoarray exhibits superior oxygen evolution reaction activity and catalytic performance, significantly reducing anodic overpotential and reaction energy consumption, thus meeting the requirements for its use under industrial-grade high-current conditions.

[0059] Similarly, taking ferric nitrate and manganese nitrate as examples, during the process of immersing the etched nickel foam in a composite salt solution of ferric nitrate and manganese nitrate, the active nickel ions on the surface of the nickel foam grow into NiFeMn-LDH nanoarrays under the action of iron ions, manganese ions and water in the solution. The NiFeMn-LDH nanoarrays have a ternary layered double hydroxide nanoarray of nickel, iron and manganese, which can provide more active sites and an excellent electronic coordination environment.

[0060] For example, the concentration of any one metal cation in the second solution is 50 μmol / ml to 100 μmol / ml. Within this concentration range, the concentration of the metal cation is moderate and can fully react with the metal ions and water on the surface of the catalytic material, thereby forming a large number of binary or ternary layered double hydroxide nanoarrays. If the concentration range is too high or too low, the growth of the layered double hydroxide nanoarrays will be inhibited.

[0061] In practice, at room temperature, nickel-based catalyst material that has undergone micron-level etching can be added to a solution of one or two nitrates (5 mmol each) of iron nitrate, manganese nitrate, chromium nitrate, and cobalt nitrate, and 100 ml of water and immersed for 6 h to 12 h to obtain a nickel-based catalyst material composite. After rinsing with deionized water several times, the composite is placed in a drying oven and dried at a constant temperature of 40 °C to 60 °C for 8 h to 16 h to obtain nanoscale modified nickel-based catalyst material such as sheet-like nickel-iron.

[0062] It should be noted that, in addition to NiFe-LDH nanoarrays and NiFeMn-LDH nanoarrays, those skilled in the art can also modify the surface of nickel-based catalytic materials with binary or ternary nickel-based layered double hydroxide nanoarrays such as NiMn-LDH, NiCo-LDH, NiCr-LDH, NiFeMn-LDH, NiFeCo-LDH, and NiFeCr-LDH based on the technical ideas of the embodiments of this disclosure, and modify the surface of iron-based catalytic materials with FeMn-LDH, FeCo-LDH, FeCr-LDH, and FeMnCo-LDH. Binary or ternary iron-based layered double hydroxide nanoarrays such as DH and FeMnCr-LDH, as well as titanium-based binary or ternary layered double hydroxide nanoarrays such as TiMn-LDH, TiCo-LDH, TiCr-LDH, TiMnFe-LDH, TiCoFe-LDH, and TiCoFe-LDH modified on the surface of titanium-based catalytic materials, and more diverse layered double hydroxide nanoarrays, are used to improve the catalytic performance of existing nickel-based, iron-based, and titanium-based water electrolysis catalytic materials and meet their application requirements under industrial-grade high-current conditions. No specific limitations are imposed here.

[0063] As described above, this disclosure provides a method for surface modification of transition metal-based water electrolysis catalysts. The method includes: first, using the transition metal-based water electrolysis catalyst to be modified as a target substrate; then, immersing the target substrate in a first solution for etching treatment to form an etched morphology on the surface of the target substrate; finally, immersing the etched target substrate in a second solution for modification treatment to grow a layered double hydroxide nanoarray on the surface of the target substrate. Because the modified transition metal-based water electrolysis catalyst has a layered double hydroxide nanoarray on its surface, compared to the smooth surface of existing transition metal-based water electrolysis catalysts, its specific surface area is increased, enhancing the exposure of its surface active sites. This facilitates sufficient contact of the electrolyte and rapid charge migration during heterogeneous water electrolysis catalysis, significantly reducing anodic overpotential and reaction energy consumption. It exhibits excellent oxygen evolution reaction activity and catalytic performance, thus meeting the requirements for use under industrial-grade high-current conditions.

[0064] Furthermore, in addition to the metal cations mentioned above, the second solution may also contain metatungstate ions. Here, metatungstate ions serve as a tungsten source, enabling the introduction of tungsten into a layered double hydroxide nanoarray modified with iron and nickel nanoparticles. This yields an atomically modified nickel-based catalytic material with high-valence tungsten cation exchange, thereby further regulating the surface electronic structure of the nickel-based catalytic material and improving its catalytic performance.

[0065] Specifically, the second solution can be a mixed solution of ammonium metatungstate and nitrate.

[0066] Taking nickel foam as an example, the modification process based on a mixed solution of ammonium metatungstate and nitrate can be understood as follows:

[0067] During the immersion process of etched nickel foam in a mixed solution of ammonium metatungstate and nitrate, the active nickel ions on the surface of the nickel foam grow into a NiFeW-LDH nanoarray under the action of iron ions, tungsten ions, and water in the solution. The NiFeW-LDH nanoarray is a ternary layered double hydroxide nanoarray containing nickel, iron, and tungsten. 4+ With W 6+ It can effectively modulate the electronic structure of active sites on the surface of nickel-based catalysts and improve their conductivity, thus exhibiting superior catalytic activity for the oxygen evolution reaction.

[0068] Figure 5 The surface morphology of NiFeW-LDH nanoarray-modified nickel foam is shown. It can be seen that the nickel foam surface is modified with a uniformly distributed NiFeW-LDH layered double hydroxide nanoarray, resulting in an increased specific surface area and enhanced exposure of active sites. This facilitates sufficient electrolyte contact and rapid charge migration during heterogeneous water electrolysis catalysis. Compared to the smooth surface of existing nickel foam, the introduction of high-valence tungsten modulates the electronic structure of active sites in the NiFeW-LDH layered double hydroxide nanoarray, providing a superior electronic coordination environment and significantly reducing the anodic overpotential, thus meeting the requirements for industrial-grade high-current applications.

[0069] For example, the molar ratio of ammonium metatungstate to nitrate can be 1:2 to 1:15. Within this molar ratio range, the proportion of tungsten ions and metal cations in nitrate is moderate, which is beneficial for the formation of NiFeW-LDH layered double hydroxide nanoarray structure and the appropriate introduction of high-valence metal tungsten. Conversely, if the proportion is too high or too low, it will inhibit the growth of NiFeW-LDH layered double hydroxide nanoarray structure, and the distribution of high-valence metal tungsten will be uneven due to too little or too much tungsten.

[0070] Furthermore, surfactants can be added to the second solution to enhance the reactivity during the modification process, thereby further forming a transition metal-based water electrolysis catalyst with uniform morphology and appropriate amount of introduction.

[0071] For example, the surfactant may be one of sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and hexadecyltrimethylammonium bromide (CTAB).

[0072] For example, the molar ratio between the sum of the amounts of ammonium metatungstate and nitrate and the amount of surfactant is 8:1 to 1:2. Within this molar ratio range, the proportions of tungsten ions, metal cations in nitrate, and surfactant are moderate, which is beneficial for the rapid formation of a large number of NiFeW-LDH layered double hydroxide nanoarray structures. Conversely, if the proportions are too high or too low, the effect on the growth of NiFeW-LDH layered double hydroxide nanoarray structures is weak.

[0073] In practice, at room temperature, nickel-based catalyst material that has undergone micron-level etching is added to a solution of ammonium metatungstate and nitrate in a molar ratio of 1:2 to 1:15 and 100 ml of water. Sodium dodecylbenzenesulfonate in a molar ratio of 8:1 to 1:2 to the sum of the two salts is then added. The solution is immersed at a constant temperature of 45℃ to 75℃ for 3, 6, and 12 hours, respectively. After immersion, the solution is removed and ultrasonicated for 3 minutes to remove excess residue, resulting in a nickel-based catalyst material composite. The composite is then rinsed several times with deionized water and placed in a drying oven at a constant temperature of 40℃ to 60℃ for 8 to 16 hours to obtain a sheet-like atomically modified nickel-based catalyst material containing high-valence tungsten cation exchange.

[0074] Furthermore, embodiments of the present invention also provide a water electrolysis catalytic material, including a transition metal-based water electrolysis catalytic material and a layered double hydroxide nanoarray modified on the surface of the transition metal-based water electrolysis catalytic material. The water electrolysis catalytic material is prepared by the surface modification method of a metal-based water electrolysis catalytic material described above.

[0075] To help those skilled in the art to better understand the surface modification method and performance advantages of the transition metal-based water electrolysis catalyst in the embodiments of this disclosure, the following embodiments of this disclosure are described with reference to specific examples.

[0076] Example 1

[0077] The transition metal-based water electrolysis catalyst in Example 1 uses pure nickel foam catalyst. NF represents nickel foam, a commercially available three-dimensional open-pore functional metal material with interconnected pores and a metal framework. It is widely used in nickel-metal hydride battery electrode materials, fuel cells, and other fields. The surface modification method of pure nickel foam catalyst includes the following steps:

[0078] (1) A 10cm×10cm piece of pure nickel foam catalyst was placed in acetone, ethanol and deionized water in sequence, ultrasonically treated for 15 minutes and then placed in a drying oven and dried at 50℃ to obtain pretreated pure nickel foam catalyst (see Figure 1 );

[0079] (2) Under room temperature conditions, the pretreated pure nickel foam catalyst was immersed in a mixed solution with a volume ratio of nitric acid and sodium hypochlorite solution of 1:1 and a volume ratio of the sum of the volumes of nitric acid and sodium hypochlorite solution to water of 1:5 for 5 min; rinsed several times with deionized water and placed in a drying oven to dry at 50℃ for 12 h to obtain micron-sized etchable pure nickel foam catalyst (HNO3+NaClO / NF) (see Figure 3 ).

[0080] (3) Under room temperature conditions, micron-sized etched pure nickel foam catalyst material was added to a solution containing 5 mmol of one or two nitrates (ferric nitrate, manganese nitrate, chromium nitrate, and cobalt nitrate) and 100 ml of water and immersed for 6 h to 12 h to obtain a pure nickel foam catalyst material composite. This composite was then rinsed several times with deionized water and placed in a drying oven at 50 °C for 12 h to obtain a sheet-like nickel-iron nanoscale modified pure nickel foam catalyst material (NiFe-LDH-6 / NF) (see...). Figure 4 ).

[0081] from Figure 1 It can be seen that existing pure nickel foam catalysts have smooth surfaces, small specific surface areas, difficulty in adsorbing water, and poor electrocatalytic hydrolysis performance.

[0082] from Figure 3 It can be seen that the micron-scale etching of pure foam nickel catalyst material (HNO3+NaClO / NF) creates pits of 2μm~10μm on the surface by mixed acid, and the etching is carried out along the grain boundaries, which increases the specific surface area and enhances the exposure of its active sites. This helps to ensure sufficient contact of the electrolyte and rapid charge migration during the heterogeneous catalysis process of water electrolysis.

[0083] from Figure 4 It can be seen that the surface of the nanoscale modified nickel-based catalytic material (NiFe-LDH-6 / NF) is modified into a layered double hydroxide nanoarray, which increases the specific surface area, enhances the exposure of its active sites, and helps to ensure sufficient contact of the electrolyte and rapid charge migration during the heterogeneous catalytic process of water electrolysis.

[0084] Example 2

[0085] The metal-based water electrolysis catalyst in Example 2 uses pure nickel foam catalyst. The surface modification method of pure nickel foam catalyst includes the following steps:

[0086] (1) A 10cm×10cm piece of pure nickel foam catalyst was placed in acetone, ethanol and deionized water in sequence, ultrasonically treated for 15 minutes and then placed in a drying oven and dried at 50℃ to obtain pretreated pure nickel foam catalyst (see Figure 1 );

[0087] (2) Under room temperature conditions, the pretreated pure nickel foam catalyst was immersed in a mixed solution with a volume ratio of nitric acid and sodium hypochlorite solution of 1:1 and a volume ratio of the sum of the volumes of nitric acid and sodium hypochlorite solution to water of 1:5 for 5 min; rinsed several times with deionized water and placed in a drying oven to dry at 50℃ for 12 h to obtain micron-sized etchable pure nickel foam catalyst (HNO3+NaClO / NF) (see Figure 3 ).

[0088] (3) Under room temperature conditions, micron-sized etched pure nickel foam catalyst material was added to a solution of ammonium metatungstate and nitrate in a molar ratio of 1:5 or 1:10 and 100 ml of water. Sodium dodecylbenzenesulfonate in molar ratios of 2:1 and 1:1 to the sum of the two salts was then added. After soaking at 60°C for 3 h, 6 h, or 12 h, the solution was removed and sonicated for 3 min to remove excess residue, resulting in a pure nickel foam catalyst material composite. This composite was rinsed several times with deionized water and dried in a drying oven at 50°C for 12 h to obtain an atomically modified pure nickel foam catalyst material (NiFeW-LDH-6 / NF) containing high-valence tungsten cation exchange (see...). Figures 5 to 7 ).

[0089] from Figure 5 It can be seen that the surface of the atomically modified pure nickel foam catalyst (NiFeW-LDH-6 / NF) is modified into a layered hydrotalcite structure, which increases the specific surface area, enhances the exposure of its active sites, and facilitates sufficient electrolyte contact and rapid charge migration during the heterogeneous catalytic process of water electrolysis. Simultaneously, the introduction of high-valence tungsten metal modulates the electronic structure of the active sites in the NiFeW-LDH layered double hydroxide nanoarray, providing a superior electronic coordination environment and significantly reducing the anodic overpotential, thus meeting the requirements for its use under industrial-grade high-current conditions.

[0090] Figure 6 The X-ray photoelectron spectroscopy in the image directly reveals the presence of high-valence tungsten, indicating the successful introduction of tungsten into the NiFeW-LDH layered double hydroxide nanoarray. Figure 7 High-valence tungsten exhibits +4 and +6 valences, which in turn regulates the electronic structure of nickel-based catalysts, giving them a superior electronic coordination environment.

[0091] Figure 8 Linear sweep voltammetric curves of pure nickel foam catalysts etched and modified at different scales are shown. Specifically, the overpotentials of pure nickel foam catalysts etched and modified at different scales at different current densities are shown in Table 1.

[0092] Table 1

[0093]

[0094] Combination Figure 8 As shown in Table 1, compared with pure nickel foam catalyst NF and micron-sized etched pure nickel foam catalyst (HNO3+NaClO / NF), nanoscale modified nickel-based catalyst (NiFe-LDH-6 / NF) and atomically modified pure nickel foam catalyst (NiFeW-LDH-6 / NF) both exhibit higher electrocatalytic oxygen evolution activity. Among them, the nanoscale modified nickel-based catalyst (NiFe-LDH-6 / NF) and the atomically modified pure nickel foam catalyst (NiFeW-LDH-6 / NF) show higher activity at 10 mA / cm². 2 The overpotentials at current densities reached 270 mV and 215 mV, respectively, significantly lower than those of the unmodified pure nickel foam catalyst NF at 10 mA / cm². 2 Overpotential at current density.

[0095] Furthermore, the atomically modified pure nickel foam catalyst (NiFeW-LDH-6 / NF) achieves a speed of 1000 mA / cm². 2 The overpotential at high current density is only 338mV, significantly lower than that of the unmodified pure nickel foam catalyst NF at 1000mA / cm. 2 The overpotential at high current density is ideal for long-term use under industrial-grade high current conditions.

[0096] Figure 9 The constant current stability test curves of pure nickel foam catalysts etched and modified at different scales are shown. Figure 9 It can be seen that, compared with pure nickel foam catalyst NF and micron-sized etched pure nickel foam catalyst (HNO3+NaClO / NF), the galvanostatic stability curves of nanoscale modified nickel-based catalyst (NiFe-LDH-6 / NF) and atomic-level modified pure nickel foam catalyst (NiFeW-LDH-6 / NF) are smoother and do not show an upward trend after 600 hours of long-term service, indicating that the modified nickel foam catalyst has better stability.

[0097] As described above, the modified transition metal-based water electrolysis catalytic material of this embodiment has controllable defects and electronic structure at the active sites. The reduction reaction of high-valence metals during the reaction process will accelerate electron transfer and increase the valence state of the active material Ni, reduce the energy barrier, and accelerate the kinetic process of water splitting, thus giving it excellent electrocatalytic hydrogen evolution performance.

[0098] Furthermore, the embodiments of this disclosure controllably prepare surface-modified multi-dimensional etching and modification of nickel-based, iron-based, and titanium-based catalytic materials through an impregnation method. The process is simple, the raw materials are readily available, the reaction is mild, fast, efficient, and suitable for large-area production. Its enormous potential value and application prospects in water electrolysis provide a research approach for the preparation of electrode materials for constructing efficient and stable alkaline electrolyzers.

[0099] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0100] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0101] Those skilled in the art should understand that the above embodiments are merely for illustrating the present disclosure and are not intended to limit the scope of the disclosure. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of the present disclosure.

Claims

1. A method for surface modification of a transition metal-based water electrolysis catalyst, characterized in that, include: The transition metal-based water electrolysis catalyst to be modified was used as the target substrate; The target substrate is immersed in a first solution for etching to form an etched morphology on the surface of the target substrate. The first solution is a mixed solution of nitric acid, sodium hypochlorite solution and water, wherein the volume ratio of nitric acid, sodium hypochlorite solution and water is 1:1:10 to 1:1:

20. The etched target substrate is immersed in a second solution for modification, and a layered double hydroxide nanoarray is grown on the surface of the target substrate to obtain a modified transition metal-based water electrolysis catalyst. The second solution contains one or more metal cations that are different from those in the target substrate: iron ions, manganese ions, cobalt ions, molybdenum ions, and chromium ions; the second solution also contains metatungstate ions. The transition metal-based water electrolysis catalyst includes any one of the following catalysts: nickel-based catalysts, iron-based catalysts, cobalt-based catalysts, and titanium-based catalysts.

2. The surface modification method according to claim 1, characterized in that, The concentration of any one metal cation in the second solution is 50 μmol / ml to 100 μmol / ml.

3. The surface modification method according to claim 1, characterized in that, The second solution is a mixed solution of ammonium metatungstate and nitrate, wherein the molar ratio of ammonium metatungstate to nitrate is 1:2 to 1:

15.

4. The surface modification method according to claim 3, characterized in that, The second solution contains a surfactant, and the ratio between the sum of the amounts of ammonium metatungstate and nitrate and the amount of the surfactant is 8:1 to 1:

2.

5. The surface modification method according to claim 4, characterized in that, The surfactant includes one of sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and hexadecyltrimethylammonium bromide (CTAB).

6. A water electrolysis catalyst, characterized in that, The invention includes a transition metal-based water electrolysis catalyst, and a layered double hydroxide nanoarray modified on the surface of the transition metal-based water electrolysis catalyst, wherein the water electrolysis catalyst is prepared by a surface modification method for a transition metal-based water electrolysis catalyst according to any one of claims 1 to 5.

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