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

Abstract

The present disclosure discloses a surface modification method for a transition metal-based catalytic material and a water electrolysis catalytic material. The surface modification method comprises: using the transition metal-based catalytic material to be modified as a target substrate; immersing the target substrate in an acidic solution for etching to form an etched morphology on the surface of the target substrate; immersing the etched target substrate in a salt solution containing at least two metal cations different from the target substrate for modification to grow a layered double hydroxide nanoarray on the surface of the target substrate; immersing the modified target substrate in an alkaline solution for alkali-induced cation dissolution to form cation vacancies on the surface of the layered double hydroxide nanoarray. The present disclosure sequentially modifies the surface of an existing transition metal-based catalytic material at multiple scales according to micrometer, nanometer, and atomic scales, thereby exposing more active sites on its surface and improving its water electrolysis catalytic performance.

Description

Technical Field

[0001] The present disclosure relates to the technical field of water electrolysis catalytic materials, and in particular to a surface modification method of a transition metal-based catalytic material and a water electrolysis catalytic material. Background Art

[0002] Hydrogen production by water electrolysis is a promising technology that uses renewable energy such as solar energy and wind energy to generate electricity to drive the reaction. The water electrolysis process includes two half-reactions, hydrogen production and oxygen production. Overpotential will be generated during the reaction, and the overpotential of the oxygen evolution reaction accounts for the major part. Since the oxygen evolution reaction (OER) on the anode involves a four-electron transfer process, its kinetics is very slow, which seriously limits the reaction rate of the overall water decomposition. In order to minimize the energy loss of equipment in energy conversion, it is urgent to develop high-efficiency and excellent catalytic materials to promote the oxygen evolution reaction process of water electrolysis, reduce the anode overpotential, and thus reduce the overall energy consumption of the alkaline electrolyzer.

[0003] At present, non-precious metals such as nickel, iron, and titanium are widely used as catalytic materials in commercial alkaline electrolyzers due to their low price, good activity in water electrolysis for hydrogen and oxygen evolution, and impurity resistance. However, due to the small number of surface active sites and poor intrinsic activity during the reaction of nickel-based, iron-based, and titanium-based water electrolysis catalytic materials, a large overpotential is required at industrial high current density, resulting in high energy consumption for water electrolysis and difficulty in meeting commercial production needs. This greatly reduces the utilization efficiency of nickel-based, iron-based, and titanium-based materials, and thus hinders their further development in actual 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 embodiments of the present disclosure provide a surface modification method for a transition metal-based catalytic material and a water electrolysis catalytic material, which can expose more active sites on the surface of the existing transition metal-based catalytic material, thereby reducing the anode overpotential and the reaction energy consumption, and meeting its use requirements under industrial-grade high current conditions.

[0005] In a first aspect, the present disclosure provides a method for surface modification of a transition metal-based catalytic material, comprising:

[0006] Using the transition metal-based catalytic material to be modified as a target substrate;

[0007] Immersing the target substrate in an acidic solution for etching to form an etching morphology on the surface of the target substrate;

[0008] The etched target substrate is immersed in a salt solution containing at least two metal cations different from those of the target substrate for modification, thereby growing a layered double hydroxide nanoarray on the surface of the target substrate;

[0009] The modified target substrate is immersed in an alkaline solution for alkaline-induced cation dissolution treatment, thereby forming cation vacancies on the surface of the layered double hydroxide nanoarray to obtain a modified transition metal-based catalytic material.

[0010] Optionally, the transition metal-based catalytic material includes any one of the following catalytic materials: nickel-based catalytic material, iron-based catalytic material, cobalt-based catalytic material and titanium-based catalytic material.

[0011] Optionally, the acidic 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.

[0012] Optionally, the metal cations in the salt solution include at least one of the first group of metal cations and at least one of the second group of cations; wherein the first group of cations includes: vanadium ions, chromium ions, manganese ions, iron ions, cobalt ions and nickel ions, and the second group of cations includes: aluminum ions, zinc ions and molybdenum ions.

[0013] Optionally, the salt solution is a composite nitrate solution containing ferric nitrate and aluminum nitrate, wherein the molar ratio of ferric nitrate to aluminum nitrate is 15:1 to 30:1.

[0014] Optionally, the alkaline solution is a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 2 mol / L to 15 mol / L.

[0015] Optionally, the alkaline solution is aqueous ammonia.

[0016] Optionally, the duration of the etching treatment is 5 minutes to 25 minutes; the duration of the modification treatment is 5 hours to 20 hours; and the duration of the activation treatment is 5 hours to 20 hours.

[0017] Optionally, before immersing the target substrate in an acidic solution for etching, the surface modification method further includes: placing the target substrate in acetone, ethanol and deionized water in sequence for ultrasonic cleaning; and placing the ultrasonically cleaned target substrate in a drying oven for heat preservation and drying.

[0018] In a second aspect, an embodiment of the present disclosure provides a water electrolysis catalytic material, comprising a transition metal-based catalytic material and a layered double hydroxide nanoarray modified on the surface of the transition metal-based catalytic material, wherein the surface of the layered double hydroxide nanoarray contains cationic vacancies, and the water electrolysis catalytic material is prepared by the surface modification method of the transition metal-based catalytic material described above.

[0019] As described above, the embodiment of the present disclosure provides a surface modification method for a transition metal-based catalytic material, and the preparation method includes: first, the transition metal-based catalytic material to be modified is used as a target substrate; then, the target substrate is immersed in an acidic solution for etching treatment to form an etched morphology on the surface of the target substrate; then, the etched target substrate is immersed in a salt solution containing at least two metal cations for modification treatment to grow a layered double hydroxide nanoarray on the surface of the target substrate; finally, the modified target substrate is immersed in an alkaline solution for alkaline-induced cation dissolution treatment to form cation vacancies on the surface of the layered double hydroxide nanoarray to obtain a modified transition metal-based catalytic material.

[0020] That is, the disclosed embodiments sequentially modify the surface of the existing transition metal-based catalytic material at the micron, nano, and atomic levels. Compared with the smooth surface of the existing transition metal-based catalytic material, on the one hand, the surface of the modified transition metal-based catalytic material is a layered double hydroxide nanoarray structure, which increases the specific surface area and enhances the exposure of its surface active sites, facilitating sufficient contact with the electrolyte and rapid charge migration during the heterogeneous catalytic process of water electrolysis, significantly reducing the anode overpotential and reaction energy consumption, and having excellent water electrolysis catalytic performance; on the other hand, vacancies are also precipitated on the surface of the layered double hydroxide nanoarray, which can further accelerate the evolution of the active sites of the catalytic material during the water-desorption oxygen reaction, while optimizing the binding energy of the water-desorption oxygen reaction intermediates on the surface of the catalytic material, further reducing the energy barrier, accelerating the kinetic process of water decomposition, and making it have more excellent water electrolysis catalytic performance, fully meeting its use requirements under industrial-grade high current conditions.

[0021] The above description is only an overview of the technical solution of the present disclosure. In order to more clearly understand the technical means of the present disclosure, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present disclosure more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 A scanning electron microscope image of a pure nickel foam catalytic material provided in an embodiment of the present disclosure;

[0024] Figure 2A flow chart of a surface modification method for a transition metal-based catalytic material provided in an embodiment of the present disclosure;

[0025] Figure 3 A scanning electron microscope image of an acid-etched pure nickel foam catalytic material provided in an embodiment of the present disclosure;

[0026] Figure 4 A scanning electron microscope image of a pure nickel foam catalytic material modified with layered double hydroxide provided in an embodiment of the present disclosure;

[0027] Figure 5 A scanning electron microscope image of a pure nickel foam catalytic material modified with a layered double hydroxide nanoarray containing iron vacancies provided in an embodiment of the present disclosure;

[0028] Figure 6 A high-resolution transmission electron microscopy image of a pure nickel foam catalytic material modified with a layered double hydroxide nanoarray containing iron vacancies provided in an embodiment of the present disclosure;

[0029] Figure 7 Linear sweep voltammetry curves of pure nickel foam catalytic materials etched and modified at different scales provided in the embodiments of the present disclosure;

[0030] Figure 8 This is a constant current stability test curve for etching and modifying nickel-based catalytic materials at different scales provided in the embodiments of the present disclosure. DETAILED DESCRIPTION

[0031] The present disclosure will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the relevant content and are not intended to limit the present disclosure. It should also be noted that, for ease of description, only the portions relevant to the present disclosure are shown in the accompanying drawings.

[0032] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in the present disclosure can be combined with each other. The technical solution of the present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] Unless otherwise stated, the exemplary embodiments / examples shown are to be understood as providing exemplary features of various details of some ways in which the technical concepts of the present disclosure can be implemented in practice. Therefore, unless otherwise stated, the features of the various embodiments / examples may be further combined, separated, interchanged, and / or rearranged without departing from the technical concepts of the present disclosure.

[0034] The terms used herein are for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, unless the context clearly indicates otherwise, the singular forms "one (kind, person)" and "said (the)" are also intended to include plural forms. In addition, when the terms "comprise" and / or "include" and their variations are used in this specification, the features, integral bodies, steps, operations, parts, assemblies and / or their groups stated are explained, but the presence or addition of one or more other features, integral bodies, steps, operations, parts, assemblies and / or their groups is not excluded. It should also be noted that, as used herein, the terms "substantially", "approximately" and other similar terms are used as approximate terms and not as degree terms, so that they are used to explain the inherent deviations of the measured values, calculated values and / or the values provided that will be recognized by those of ordinary skill in the art.

[0035] Currently, non-precious metal-based catalytic materials, such as nickel-, iron-, and titanium-based catalytic materials, are widely used in commercial alkaline electrolyzers. These cells typically operate at relatively high current densities. For example, nickel-based catalytic materials, including nickel plates, nickel mesh, and nickel foam, require large overpotentials at high industrial current densities, hindering their further development in practical industrial applications.

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

[0037] The inventors considered providing more active sites and a better electron coordination environment by modifying its surface, reducing the reaction overpotential, and thus reducing the reaction energy consumption, improving its catalytic performance, and meeting its use requirements under industrial-grade high-current conditions, thereby developing a highly active, low-cost, long-term stable water electrolysis catalytic material suitable for industrial-grade high-current conditions.

[0038] Based on this, the present disclosure provides a surface modification method for transition metal-based catalytic materials, which can be used to modify the surface of existing commercial nickel-, iron-, and titanium-based catalytic materials. Existing commercial metal-based water electrolysis catalytic materials all belong to the transition metal family. Compared with precious metal-based water electrolysis catalytic materials, transition metal-based catalytic materials offer the advantages of moderate price and excellent catalytic performance, and are commonly used in commercial alkaline electrolyzers.

[0039] See Figure 2 The surface modification method of the transition metal-based catalytic material provided in the embodiment of the present disclosure includes steps S1 to S4.

[0040] S1. Using the transition metal-based catalytic material to be modified as the target substrate.

[0041] Illustratively, the transition metal-based catalytic material to be modified includes any one of the following catalytic materials: nickel-based catalytic materials, iron-based catalytic materials, cobalt-based catalytic materials, and titanium-based catalytic materials. Nickel-based catalytic materials may include nickel plates, nickel mesh, and nickel foam; iron-based catalytic materials may include iron plates, iron mesh, and iron foam; titanium-based catalytic materials may include titanium plates, titanium mesh, and titanium foam; and cobalt-based catalytic materials may include cobalt plates, cobalt mesh, and cobalt foam.

[0042] In specific implementation, the metal-based water electrolysis catalytic material to be modified can be pretreated first, and the target substrate can be placed in acetone, ethanol and deionized water for ultrasonic cleaning in turn to remove dust, organic matter, inorganic matter and other impurities on its surface, and then the target substrate after ultrasonic cleaning can be placed in a drying oven for heat preservation and drying.

[0043] For example, a 10 cm×10 cm nickel-based catalytic material can be placed in acetone, ethanol and deionized water in sequence and ultrasonically treated for 10 to 25 minutes, and then placed in a drying oven at a constant temperature of 40° C. to 60° C. for drying before use.

[0044] S2. Immersing the target substrate in an acidic solution for etching to form an etching morphology on the surface of the target substrate.

[0045] Specifically, the acidic solution can be a mixed solution of nitric acid, sodium hypochlorite solution, and water. The sodium hypochlorite solution is obtained by absorbing chlorine gas into sodium hydroxide, and contains a large amount of chloride ions and hypochlorite ions. It should be noted that both nitric acid and sodium hypochlorite solution can be industrial standard products and do not require additional preparation.

[0046] Taking nickel-based catalytic materials as an example, the corrosion treatment process in step S2 can be understood as follows:

[0047] During the immersion of nickel-based catalytic materials in a mixed solution of nitric acid, sodium hypochlorite solution and water, the violent oxidation reaction of chloride ions, the violent reduction reaction of hypochlorite ions and the strong oxidizing property of nitrate ions in the solution will etch the surface of the nickel-based catalytic material, forming a micron-scale etching morphology, thereby achieving micron-scale etching of the transition metal-based catalytic material and providing a good active substrate for the modified growth of nickel-based nanoarrays.

[0048] 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 relatively ideal etching morphology on the surface of the nickel-based catalytic material, thereby providing a good active substrate for the growth of the nanoarray structure. Conversely, excessively high or low concentrations of chloride ions, hypochlorite ions, and nitrate ions will inhibit the etching reaction.

[0049] For example, the etching time can be 3 to 8 minutes. Within this time range, the chloride, hypochlorite, and nitrate ions etch the nickel-based catalytic material surface for a moderate amount of time, forming a relatively ideal etched morphology on the nickel-based catalytic material surface, thereby providing a good active substrate for the growth of the nanoarray structure. Conversely, if the chloride, hypochlorite, and nitrate ion etching time is too high or too low, the nickel-based catalytic material will dissolve or the etching depth will be insufficient.

[0050] In a specific implementation, the pretreated nickel-based catalytic material can be immersed in a mixed solution of nitric acid and sodium hypochlorite solution in a volume ratio of 1:1 and a mixed solution of the sum of the volumes of nitric acid and sodium hypochlorite solution to water in a volume ratio of 1:5 to 1:10 at room temperature for 3 to 8 minutes. After being taken out, it is rinsed with deionized water several times and placed in a drying oven for constant temperature drying at 30° C. to 70° C. for 8 to 16 hours to obtain a micron-level etching nickel-based catalytic material.

[0051] S3, immersing the target substrate after the etching treatment in a salt solution containing at least two metal cations different from the target substrate for modification treatment, and growing a layered double hydroxide nanoarray on the surface of the target substrate.

[0052] Among them, layered double hydroxide (LDH) is a metal hydroxide composed of two or more metal elements. It has the advantages of easy composition adjustment, easy structure tailoring, and easy compounding with other materials to achieve functionalization. It is widely used in energy conversion and electrochemical energy storage such as supercapacitors, secondary batteries and electrocatalysis. Specifically, layered double hydroxide as a catalyst is composed of positively charged (M 2+ ,M 3+ It is composed of )(OH)6 octahedral main layers and negatively charged anions and water molecules between the layers. Its active sites mainly exist in the active metal ions on the layers.

[0053] Illustratively, the metal cations in the salt solution used for modification treatment in step S3 include at least one of the first group of metal cations and at least one of the second group of cations; wherein the first group of cations includes: vanadium ions, chromium ions, manganese ions, iron ions, cobalt ions and nickel ions, and the second group of cations includes: aluminum ions, zinc ions and molybdenum ions.

[0054] Taking the target substrate as a nickel-based catalytic material as an example, and the anions in the salt solution are nitrate ions, the salt solution used for modification treatment can be a composite nitrate solution formed by at least one of vanadium nitrate, chromium nitrate, manganese nitrate, iron nitrate and cobalt nitrate, and at least one of aluminum nitrate, zinc nitrate and molybdenum nitrate.

[0055] For example, if the target substrate is a nickel-based catalytic material and the salt solution used for the modification treatment is a composite nitrate solution of iron nitrate and aluminum nitrate, the modification treatment process in step S3 can be understood as follows:

[0056] After the etched nickel-based catalytic material is immersed in ferric nitrate and aluminum nitrate solutions for a period of time, the active nickel ions on the surface of the nickel-based catalytic material symbiotically form a layered double hydroxide structure under the action of iron ions, aluminum ions and water in the solution. Among them, trivalent aluminum ions fill part of the positions in the array that were originally trivalent iron ions during the symbiotic growth process, and finally form a layered ternary double hydroxide NiFeAl-LDH nanoarray containing nickel, iron and aluminum, thereby realizing nanoscale modification of the transition metal-based catalytic material.

[0057] Here, the NiFeAl-LDH nanoarrays are evenly distributed on the surface of the nickel-based catalyst material, increasing the specific surface area of the nickel-based catalyst material and enhancing the exposure of the surface active sites. This facilitates sufficient contact with the electrolyte and rapid charge transfer during the heterogeneous catalytic process of water electrolysis. Compared to the smooth surface of existing nickel-based catalyst materials, the nickel-based catalyst material modified with the NiFeAl-LDH nanoarrays exhibits excellent oxygen evolution reaction activity and catalytic performance.

[0058] For example, the molar ratio of ferric nitrate to aluminum nitrate in the composite nitrate solution can be 15:1 to 30:1. Within this range, the molar ratio of iron ions is much greater than that of aluminum ions. This is because a large amount of iron ions and nitrate ions can further etch out nickel ions, thereby increasing the amount of active nickel ions and forming more NiFeAl-LDH layered ternary hydroxide nanoarrays.

[0059] For example, the etching treatment time can be 5 to 20 hours. Within this time range, iron ions, aluminum ions, and nitrate ions can fully etch out nickel ions under the action of water, and as the number of active nickel ions increases, more NiFeAl-LDH layered ternary hydroxide nanoarrays are formed. Conversely, if the modification treatment time is too low, it is easy to cause the nickel-based catalytic material to dissolve or the etching depth to be insufficient, and if it is too high, it is easy to cause changes in the generated NiFeAl-LDH layered ternary hydroxide nanoarray.

[0060] In specific implementation, the nickel-based catalytic material after micron-level etching in step S2 can be added to a composite nitrate of iron nitrate and aluminum nitrate with a molar ratio of 25:1 at room temperature and immersed for 12 hours to obtain a nickel-based catalytic material complex, which is then rinsed with deionized water several times and placed in a drying oven and dried at a constant temperature of 50°C for 12 hours to obtain a flaky nickel-iron-aluminum nano-scale modified nickel-based catalytic material.

[0061] Similarly, taking the target substrate as a nickel-based catalytic material and the salt solution used for modification treatment as a composite nitrate solution of iron nitrate and zinc nitrate as an example, during the immersion of the etched nickel-based catalytic material in the composite salt solution of iron nitrate and zinc nitrate, divalent zinc ions filled into some of the positions in the array that were originally divalent nickel ions during the co-growth process, and grew a layered ternary hydroxide NiFeZn-LDH nanoarray containing nickel, iron and zinc.

[0062] S4. Immersing the modified target substrate in an alkaline solution for alkaline-induced cation dissolution treatment to form cation vacancies on the surface of the layered double hydroxide nanoarray to obtain a modified transition metal-based catalytic material.

[0063] Taking NiFeAl-LDH and NiFeZn-LDH nanoarrays as examples, the activation process in step S4 can be understood as follows:

[0064] Due to the low activity of zinc and aluminum, the trivalent aluminum ions in NiFeAl-LDH and the divalent zinc ions in NiFeZn-LDH are easily precipitated in alkaline solutions. During the co-growth process, the trivalent aluminum ions fill some of the array's positions that were originally occupied by trivalent iron ions, and the divalent zinc ions fill some of the array's positions that were originally occupied by divalent nickel ions. Consequently, the resulting vacancies are those of trivalent iron ions and divalent nickel ions, thereby achieving atomic-level modification of the transition metal-based catalytic material. These vacancies can further accelerate the evolution of Ni active sites during the water-to-oxygen splitting reaction, while also optimizing the binding energy of the water-to-oxygen splitting reaction intermediates on the catalytic material surface, reducing the energy barrier and accelerating the kinetics of water splitting, resulting in excellent electrocatalytic hydrogen evolution performance.

[0065] For example, the alkaline solution may be sodium hydroxide, and the concentration of the sodium hydroxide solution may be 2 mol / L to 15 mol / L. Within this concentration range, the concentration of hydroxide ions is moderate, which is conducive to the precipitation of a large number of metal cation vacancies.

[0066] For example, the alkaline solution may also be aqueous ammonia. Those skilled in the art may select a suitable alkaline solution according to actual conditions, and the present invention is not limited thereto.

[0067] For example, the activation treatment time can be 5 to 20 hours. Within this time range, trivalent aluminum ions and divalent zinc ions can be fully precipitated under the action of hydroxide ions in the solution, forming more trivalent iron ion vacancies and divalent nickel ion vacancies. Conversely, if the activation treatment time is too short, the number of vacancies precipitated may be insufficient, while if it is too long, the precipitated vacancies may change.

[0068] In specific implementation, the flaky nickel-iron-aluminum nano-scale modified nickel-based catalytic material obtained in the above steps can be added to a 6 mol / L sodium hydroxide solution and immersed for 12 hours, then taken out, rinsed with deionized water several times, and placed in a drying oven at a constant temperature of 50°C for 12 hours to obtain an atomic-level modified nickel-based catalytic material containing iron vacancies.

[0069] It should be noted that, in addition to NiFeAl-LDH nanoarrays and NiFeZn-LDH nanoarrays, those skilled in the art can also modify the surface of nickel-based catalytic materials and iron-based catalytic materials based on the technical ideas of the embodiments of the present disclosure to form layered ternary hydroxide nanoarrays such as NiFeMn-LDH, NiFeCr-LDH, CoFeAl-LDH and CoFeZn-LDH, and immerse them in an alkaline solution to form cationic vacancies to improve the electrocatalytic hydrogen evolution performance of existing nickel-based, iron-based and titanium-based water electrolysis catalytic materials to meet their use requirements under industrial-grade high current conditions, which is not limited here.

[0070] As described above, the embodiment of the present disclosure provides a surface modification method for a transition metal-based catalytic material, and the preparation method includes: first, the transition metal-based catalytic material to be modified is used as a target substrate; then, the target substrate is immersed in an acidic solution for etching treatment to form an etched morphology on the surface of the target substrate; then, the etched target substrate is immersed in a salt solution containing at least two metal cations for modification treatment to grow a layered double hydroxide nanoarray on the surface of the target substrate; finally, the modified target substrate is immersed in an alkaline solution for alkaline-induced cation dissolution treatment to form cation vacancies on the surface of the layered double hydroxide nanoarray to obtain a modified transition metal-based catalytic material.

[0071] That is to say, the disclosed embodiments sequentially modify the surface of the existing transition metal-based catalytic material at the micron, nanometer and atomic levels. Compared with the smooth surface of the existing transition metal-based catalytic material, on the one hand, the surface of the transition metal-based catalytic material after multi-dimensional scale modification is a layered double hydroxide nanoarray structure, which increases the specific surface area and enhances the exposure of its surface active sites, which contributes to the full contact of the electrolyte and the rapid migration of charge during the heterogeneous catalytic process of water electrolysis, can significantly reduce the anode overpotential, reduce the reaction energy consumption, and have excellent water electrolysis catalytic performance; on the other hand, the surface of the layered double hydroxide nanoarray also precipitates vacancies, which can further accelerate the evolution of the active sites of the catalytic material during the water decomposition and oxygen reaction, while optimizing the binding energy of the water decomposition and oxygen reaction intermediates on the surface of the catalytic material, further reducing the energy barrier, accelerating the kinetic process of water decomposition, and making it have more excellent water electrolysis catalytic performance, fully meeting its use requirements under industrial-grade high current conditions.

[0072] In addition, the embodiments of the present disclosure also provide a water electrolysis catalytic material, including a transition metal-based catalytic material and a layered double hydroxide nanoarray modified on the surface of the transition metal-based catalytic material, wherein the surface of the layered double hydroxide nanoarray contains cationic vacancies, and the water electrolysis catalytic material is prepared by the surface modification method of the transition metal-based catalytic material described above.

[0073] In order to facilitate those skilled in the art to more clearly understand the surface modification method of the transition metal-based catalytic material and its performance advantages in the embodiments of the present disclosure, the embodiments of the present disclosure are described below with specific examples.

[0074] The transition metal-based catalytic material in this embodiment is a pure nickel foam catalytic material. NF stands for nickel foam catalytic material (nickle foam), which is a commercial three-dimensional open-pore functional metal material with interconnected pores and metal skeleton. It is widely used in nickel-hydrogen battery electrode materials, fuel cells, water electrolysis catalysis and other fields. The surface modification method of pure nickel foam catalytic material based on multi-dimensional scale includes the following steps:

[0075] (1) A 10 cm × 10 cm pure nickel foam catalyst material was placed in acetone, ethanol and deionized water in turn, ultrasonically treated for 15 min, and then placed in a drying oven and dried at a constant temperature of 50 ° C to obtain a pretreated pure nickel foam catalyst material (see Figure 1 ).

[0076] (2) Under room temperature conditions, the pretreated pure nickel foam catalyst material was immersed in a mixed solution of nitric acid and sodium hypochlorite solution with a volume ratio of 1:1 and a mixed solution of the sum of the volume of nitric acid and sodium hypochlorite solution and water with a volume ratio of 1:5 for 5 minutes; rinsed with deionized water several times and placed in a drying oven at a constant temperature of 50°C for 12 hours to obtain a micron-scale etched pure nickel foam catalyst material (HNO3+NaClO / NF) (see Figure 3 ).

[0077] (3) Under room temperature, the micron-etched nickel foam catalyst material was added to a composite nitrate of iron nitrate and aluminum nitrate with a molar ratio of 25:1 and immersed for 12 hours to obtain a nickel-based catalyst material composite. The composite was then rinsed with deionized water several times and placed in a drying oven at a constant temperature of 50°C for 12 hours to obtain a sheet-like nickel-iron-aluminum nano-scale modified nickel foam catalyst material (NiFe-LDH-12 / NF) (see Figure 4 ).

[0078] (4) The nickel-iron-aluminum nano-scale modified nickel foam catalyst material was added to a 6 mol / L sodium hydroxide solution and immersed for 12 h. After that, it was taken out and rinsed with deionized water several times. Then, it was placed in a drying oven and dried at a constant temperature of 50 ° C for 12 h to obtain an atomic-level modified nickel foam catalyst material containing iron vacancies (NiFe vac -LDH-12 / NF)(See Figure 5 and Figure 6 ).

[0079] from Figure 1 It can be seen that the existing pure nickel foam catalytic material has a smooth surface, a small specific surface area, is difficult to adsorb water, and has poor electrocatalytic hydrolysis performance.

[0080] from Figure 3 It can be seen that the surface of pure nickel foam is etched by mixed acid to form pits of 2μm-10μm, and the etching is carried out along the grain boundaries, which increases the specific surface area and enhances the exposure of active sites on the surface of nickel foam, which is conducive to sufficient contact with the electrolyte and rapid charge migration during the heterogeneous catalysis of water electrolysis.

[0081] from Figure 4 The uniformly distributed NiFeAl-LDH nanoarrays on the surface of pure nickel foam increase the specific surface area of the foam, enhance the exposure of active sites on the surface, and facilitate sufficient electrolyte contact and rapid charge transfer during heterogeneous water electrolysis. Compared to the smooth surface of existing nickel foam, the NiFeAl-LDH-modified nickel foam exhibits superior oxygen evolution reaction activity and catalytic performance.

[0082] from Figure 5 and Figure 6It can be seen that there are cationic vacancies on the surface of the atomic-level modified pure nickel foam catalytic material. These vacancies can further accelerate the evolution of the active sites of the catalytic material during the water-oxygen decomposition reaction, while optimizing the binding energy of the water-oxygen decomposition reaction intermediates on the surface of the catalytic material, further reducing the energy barrier, and accelerating the kinetic process of water decomposition, so that it has better electrocatalytic hydrogen evolution performance.

[0083] Figure 7 The linear sweep voltammetry curves of pure nickel foam catalytic materials etched and modified at different scales are shown. Specifically, the overpotentials of pure nickel foam catalytic materials etched and modified at different scales at different current densities are shown in Table 1.

[0084] Table 1

[0085]

[0086] Combine Figure 7 As can be seen from Table 1, compared with pure nickel foam catalytic material NF and micron-scale etched pure nickel foam catalytic material (HNO3+NaClO / NF), nanoscale modified pure nickel foam catalytic material (NiFe-LDH-12 / NF) and atomic-scale modified pure nickel foam catalytic material containing iron vacancies (NiFe vac -LDH-12 / NF) have high electrocatalytic oxygen evolution activity. Among them, the nano-scale modified pure nickel foam catalytic material (NiFe-LDH-12 / NF) and the atomic-scale modified pure nickel foam catalytic material containing iron vacancies (NiFe vac -LDH-12 / NF) at 10 mA / cm 2 The overpotentials at the current density were 270mV and 230mV, respectively, which were significantly lower than those of the unmodified pure nickel foam catalytic material NF at 10mA / cm 2 Overpotential at current density.

[0087] Moreover, the atomic-level modified pure nickel foam catalytic material (NiFe vac -LDH-12 / NF) at 1000mA / cm 2 The overpotential at high current density is only 369mV, which is significantly lower than that of the unmodified pure nickel foam catalytic material NF at 1000mA / cm 2 The overpotential at high current density is very suitable for long-term use under industrial-grade high current conditions.

[0088] Figure 8 Shows the etching and modification of pure nickel foam catalytic materials at different scales at 500mA / cm 2 Stability test curve under larger constant current. Figure 8It can be seen that compared with pure nickel foam catalytic material NF and micron-scale etched pure nickel foam catalytic material (HNO3+NaClO / NF), nanoscale modified nickel-based catalytic material (NiFe-LDH-12 / NF) and atomic-scale modified pure nickel foam catalytic material (NiFe vac -LDH-12 / NF) at 500mA / cm 2 The stability curves under larger constant currents were smoother and showed no upward trend after 400 h of long-term service, indicating that the modified nickel foam catalytic material had better stability.

[0089] As described above, the modified transition metal-based catalytic material of the embodiment of the present disclosure has an electronic structure with controllable vacancy defects. These vacancies can further accelerate the evolution of the active sites of the catalytic material during the water-oxygen decomposition reaction, while optimizing the binding energy of the water-oxygen decomposition reaction intermediates on the surface of the catalytic material, further reducing the energy barrier, accelerating the kinetic process of water decomposition, and making it have better electrocatalytic hydrogen evolution performance.

[0090] Moreover, the disclosed embodiments controllably prepare surface-modified multi-dimensional scale etching and modified 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-scale production. The huge potential value and application prospects in water electrolysis provide research ideas for the construction of efficient and stable alkaline electrolytic cell electrode material preparation.

[0091] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine different embodiments / methods or examples described in this specification and the features of different embodiments / methods or examples, unless they are contradictory.

[0092] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0093] Those skilled in the art will appreciate that the above embodiments are merely intended to clearly illustrate the present disclosure and are not intended to limit the scope of the present disclosure. Other changes or modifications may be made based on the above disclosure, and such changes or modifications are still within the scope of the present disclosure.

Claims

1. A surface modification method for a transition metal-based catalytic material, characterized in that: include: Using the transition metal-based catalytic material to be modified as a target substrate; Immersing the target substrate in an acidic solution for etching to form a micron-scale etching morphology on the surface of the target substrate, wherein the acidic solution is a mixed solution of nitric acid, sodium hypochlorite solution, and water, wherein the volume ratio of the nitric acid, sodium hypochlorite solution, and water is 1:1:10 to 1:1:20, and the etching treatment lasts for 5 minutes to 25 minutes; At room temperature, the etched target substrate is immersed in a salt solution containing at least two metal cations different from those of the target substrate for modification, thereby growing a layered double hydroxide nanoarray on the surface of the target substrate; Immersing the modified target substrate in an alkaline solution for alkaline-induced cation dissolution treatment to form cation vacancies on the surface of the layered double hydroxide nanoarray to obtain a modified transition metal-based catalytic material, wherein the alkaline solution is a sodium hydroxide solution with a concentration of 2 mol / L to 15 mol / L; The transition metal-based catalytic material is selected from any one of the following catalytic materials: nickel-based catalytic material, iron-based catalytic material, cobalt-based catalytic material and titanium-based catalytic material; wherein the nickel-based catalytic material is selected from nickel plate, nickel mesh and nickel foam; the iron-based catalytic material is selected from iron plate, iron mesh and iron foam; the cobalt-based catalytic material is selected from cobalt plate, cobalt mesh and cobalt foam; the titanium-based catalytic material is selected from titanium plate, titanium mesh and titanium foam; The metal cations in the salt solution are selected from at least one of the first group of metal cations and at least one of the second group of cations; wherein the first group of cations is selected from: vanadium ions, chromium ions, manganese ions, iron ions, cobalt ions and nickel ions, and the second group of cations is selected from: aluminum ions, zinc ions and molybdenum ions, and the molybdenum ions are provided by molybdenum nitrate.

2. The surface modification method according to claim 1, characterized in that The salt solution is a composite nitrate solution containing ferric nitrate and aluminum nitrate, wherein the molar ratio of the ferric nitrate to the aluminum nitrate is 15:1 to 30:

1.

3. The surface modification method according to claim 1, wherein The modification treatment lasts for 5 to 20 hours; The duration of the alkali-induced cation dissolution treatment is 5 h to 20 h.

4. The surface modification method according to claim 1, wherein Before immersing the target substrate in an acidic solution for etching, the surface modification method further comprises: The target substrate is sequentially placed in acetone, ethanol and deionized water for ultrasonic cleaning; The target substrate after ultrasonic cleaning is placed in a drying oven for heat preservation and drying.

5. A water electrolysis catalytic material, characterized in that: The invention comprises a transition metal-based catalytic material and a layered double hydroxide nanoarray modified on the surface of the transition metal-based catalytic material, wherein the surface of the layered double hydroxide nanoarray contains cationic vacancies, and the water electrolysis catalytic material is prepared by the surface modification method of the transition metal-based catalytic material according to any one of claims 1 to 4.

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