Foamed nickel composite catalyst and application thereof in water electrolysis hydrogen production

Abstract

The invention relates to a foamed nickel composite catalyst and application thereof in water electrolysis hydrogen production, and belongs to the technical field of water electrolysis hydrogen production. The composite catalyst takes foamed nickel as a three-dimensional conductive skeleton, a surface oxide layer and impurities are removed through grading pretreatment, a nitrogen-doped graphene layer is grown on the surface of the foamed nickel through a chemical vapor deposition method, and superfine nickel-cobalt alloy nanoparticles are loaded between the graphene layers through a citric acid complexing-hydrogen reduction method. According to the catalyst, the graphene electronic structure is optimized through nitrogen atom doping, and the hydrogen adsorption / desorption dynamic performance is remarkably improved by combining the d-band center matching effect of nickel-cobalt alloy; metal particle nanocrystallization is realized through the steric hindrance effect of citric acid, and agglomeration is inhibited; and the electron mobility is remarkably improved through the design of the double conductive networks.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production by electrolysis of water, and relates to a foamed nickel composite catalyst and application thereof in hydrogen production by electrolysis of water. Background Art

[0002] As a core component of the hydrogen energy industry chain, large-scale commercial application of water electrolysis hydrogen production technology remains limited by the comprehensive performance bottleneck of catalysts. First, while precious metal catalysts such as platinum and iridium exhibit low overpotentials and excellent stability in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), their resource scarcity leads to high costs, making it difficult to support the sustainable development of the hydrogen economy. While non-precious metal catalysts offer significant cost reductions, they suffer from rapid activity decay, poor conductivity, and insufficient stability, hindering their industrial application.

[0003] Nickel foam, a substrate material with a large specific surface area, shows great potential for composite catalyst applications. However, existing nickel foam composite catalysts still face technical challenges such as easy shedding of active materials, insufficient conductivity, and metal particle agglomeration. Therefore, developing nickel foam-based composite catalysts that combine high activity, high stability, and low cost has become a key scientific issue in promoting the industrialization of hydrogen production technology through water electrolysis. Summary of the Invention

[0004] The invention provides a foamed nickel composite catalyst and application thereof in hydrogen production by electrolysis of water, which has excellent electrocatalytic activity.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A foamed nickel composite catalyst comprises a foamed nickel substrate, a nitrogen-doped graphene carbon layer deposited on the foamed nickel substrate by CVD, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped carbon layer.

[0006] A method for preparing a foamed nickel composite catalyst, wherein the specific steps of the preparation method are as follows: S2-1: The nickel foam was ultrasonically cleaned with a 1 M hydrochloric acid solution for 10 to 20 minutes, and then ultrasonically cleaned with deionized water and anhydrous ethanol for 5 to 15 minutes, respectively. The nickel foam was then dried in a vacuum drying oven at 60°C for 12 to 16 hours to obtain a nickel foam substrate. S2-2: placing the nickel foam substrate in a CVD tube furnace, raising the temperature to 800-1000°C, introducing a NH3 / CH4 / H2 / Ar mixed gas, maintaining the temperature for 10-30 minutes, and then naturally cooling to room temperature to obtain a CVD-treated nickel foam; S2-3: Nickel nitrate and cobalt nitrate are mixed and dissolved in deionized water, citric acid is added, and ultrasonic treatment is performed for 30 to 60 minutes. The foamed nickel after CVD treatment is added and ultrasonic treatment is performed for 30 minutes. The sample is then vacuum dried at 80°C for 10 to 12 hours. The dried sample is heated to 500 to 600°C in an Ar / H2 mixed gas and kept warm for 2 hours to obtain the foamed nickel composite catalyst.

[0007] Furthermore, the porosity of the nickel foam in S2-1 is 90% to 95%.

[0008] Furthermore, the volume ratio of the NH3 / CH4 / H2 / Ar mixed gas in S2-2 is 1:5:25:100.

[0009] Furthermore, the volume ratio of the Ar / H2 mixed gas in S2-3 is 9:1.

[0010] Furthermore, the nickel nitrate and cobalt nitrate in S2-3 are mixed in a molar ratio of (1-3):1.

[0011] Furthermore, citric acid is added to the S2-3 in an amount equal to the mole of nickel nitrate.

[0012] The invention discloses an application of a foamed nickel composite catalyst, wherein the foamed nickel composite catalyst can be applied in the field of hydrogen production by electrolysis of water.

[0013] The nickel foam substrate provides a three-dimensional conductive skeleton, ensuring the mechanical stability and high specific surface area of the catalyst. The hydrochloric acid, deionized water and ethanol pretreatment steps can effectively remove impurities such as surface oxides, while the deionized water washing prevents residual Cl - The rapid volatility of anhydrous ethanol can avoid the local agglomeration of the carbon layer caused by water stains.

[0014] Subsequently, in the synthesis of nitrogen-doped graphene carbon layers, NH₃, a nitrogen source, decomposes into active nitrogen atoms at 800–1000°C. The carbon atoms generated by the cracking of CH₄ are deposited on the surface of the nickel foam, forming the graphene lattice. Nitrogen atoms are then incorporated into the graphene six-membered rings through substitutional doping. The H₂ / Ar gas mixture not only acts as a reducing atmosphere to inhibit oxidation of the nickel foam, but also controls the defect density of the carbon layer by adjusting the H₂ ratio. The appropriate amount of H₂ etches the amorphous carbon, exposing more active sites at the graphene edge, while Ar acts as a carrier gas to ensure uniformity of the reaction atmosphere, ultimately resulting in the formation of nitrogen-doped graphene layers. Nitrogen atoms have a higher electronegativity than carbon, leading to the accumulation of positive charges on adjacent carbon atoms and enhanced adsorption of reaction intermediates. At a certain nitrogen doping level, the electrical conductivity of the carbon layer is enhanced, forming a vertical conductive network with the nickel foam, improving electron mobility and reducing interfacial resistance. Nitrogen atoms also serve as Lewis base sites, increasing the density of active sites for the catalyst.

[0015] When nickel-cobalt composite nanoparticles are generated in situ on the surface of the graphene carbon layer, nickel nitrate / cobalt nitrate forms a stable complex under the action of citric acid, and the cavitation effect generated by ultrasonic treatment promotes the penetration of the complex into the graphene interlayer. Citric acid limits the growth of crystal nuclei through steric hindrance, and the metal salt is reduced to NiCo composite nanoparticles in an Ar / H2 atmosphere. The difference in d-band centers between Ni and Co leads to electron redistribution, optimizing the adsorption energy of intermediates and reducing the reaction energy barrier. In addition, the present invention replaces traditional precious metal catalysts such as Pt and Pd with a Ni / Co non-precious metal system, effectively reducing the cost of water electrolysis hydrogen production catalysts.

[0016] Beneficial effects of the present invention: The present invention uses nickel foam as the base material, introduces NH3 / CH4 / H2 / Ar mixed gas in the CVD process to deposit nitrogen-doped graphene layers on the surface of nickel foam, optimizes the graphene electronic structure by nitrogen atom substitution doping, combines H2 etching to control the defect density, and exposes high-density active edge sites; then utilizes the strong coordination effect of citric acid and metal ions to uniformly disperse Ni between the graphene layers. 2+ / Co 2+ NiCo composite nanoparticles were prepared by H2 reduction, and the metal-carbon layer interface bonding was enhanced by thermal carbonization with citric acid. The electronic structure regulation of nickel-cobalt composite nanoparticles significantly reduced the hydrogen evolution overpotential of the catalyst in alkaline medium. DETAILED DESCRIPTION

[0017] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments. Example

[0018] A foamed nickel composite catalyst comprises a foamed nickel substrate, a nitrogen-doped graphene carbon layer deposited on the foamed nickel substrate by CVD, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped carbon layer.

[0019] A method for preparing a foamed nickel composite catalyst, wherein the specific steps of the preparation method are as follows: S2-1: A nickel foam with a porosity of 93% was ultrasonically cleaned with a 1 M hydrochloric acid solution for 15 minutes, then ultrasonically cleaned with deionized water and anhydrous ethanol for 10 minutes each, and then dried in a vacuum drying oven at 60°C for 14 hours to obtain a nickel foam substrate. S2-2: The nickel foam substrate was placed in a CVD tube furnace, heated to 900°C, and introduced with a NH3 / CH4 / H2 / Ar mixed gas with a volume ratio of 1:5:25:100. The mixture was kept at this temperature for 20 minutes, and then naturally cooled to room temperature to obtain a nickel foam after CVD treatment. S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 2:1 and dissolved in deionized water, citric acid in an amount equal to the nickel nitrate was added, ultrasonic treatment was performed for 45 minutes, CVD-treated nickel foam was added, ultrasonic treatment was performed for 30 minutes, and then vacuum dried at 80°C for 11 hours. The dried sample was heated to 550°C in an Ar / H2 mixed gas with a volume ratio of 9:1 and kept warm for 2 hours to obtain the foam nickel composite catalyst. Example

[0020] A foamed nickel composite catalyst comprises a foamed nickel substrate, a nitrogen-doped graphene carbon layer deposited on the foamed nickel substrate by CVD, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped carbon layer.

[0021] A method for preparing a foamed nickel composite catalyst, wherein the specific steps of the preparation method are as follows: S2-1: A nickel foam with a porosity of 90% was ultrasonically cleaned with a 1 M hydrochloric acid solution for 10 minutes, then ultrasonically cleaned with deionized water and anhydrous ethanol for 5 minutes each, and then dried in a vacuum drying oven at 60°C for 12 hours to obtain a nickel foam substrate; S2-2: The nickel foam substrate was placed in a CVD tube furnace, heated to 800°C, and introduced with a mixed gas of NH3 / CH4 / H2 / Ar at a volume ratio of 1:5:25:100. The mixture was kept at this temperature for 10 minutes, and then naturally cooled to room temperature to obtain a nickel foam after CVD treatment. S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 1:1 and dissolved in deionized water, citric acid in an amount equal to the nickel nitrate was added, and ultrasonic treatment was performed for 30 minutes. The foamed nickel after CVD treatment was added and ultrasonic treatment was performed for 30 minutes. The sample was then vacuum dried at 80°C for 10 hours. The dried sample was heated to 500°C in an Ar / H2 mixed gas with a volume ratio of 9:1 and kept warm for 2 hours to obtain the foamed nickel composite catalyst. Example

[0022] A foamed nickel composite catalyst comprises a foamed nickel substrate, a nitrogen-doped graphene carbon layer deposited on the foamed nickel substrate by CVD, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped carbon layer.

[0023] A method for preparing a foamed nickel composite catalyst, wherein the specific steps of the preparation method are as follows: S2-1: A nickel foam with a porosity of 95% was ultrasonically cleaned with a 1 M hydrochloric acid solution for 20 minutes, then ultrasonically cleaned with deionized water and anhydrous ethanol for 15 minutes each, and then dried in a vacuum drying oven at 60°C for 16 hours to obtain a nickel foam substrate. S2-2: Placing the nickel foam substrate in a CVD tube furnace, heating it to 1000°C, introducing a mixed gas of NH3 / CH4 / H2 / Ar with a volume ratio of 1:5:25:100, keeping the temperature for 30 minutes, and then naturally cooling it to room temperature to obtain a nickel foam after CVD treatment; S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 3:1 and dissolved in deionized water, citric acid in an amount equal to the nickel nitrate was added, ultrasonic treatment was performed for 60 min, CVD-treated nickel foam was added, ultrasonic treatment was performed for 30 min, and then vacuum dried at 80°C for 12 h. The dried sample was heated to 600°C in an Ar / H2 mixed gas with a volume ratio of 9:1 and kept warm for 2 h to obtain the foam nickel composite catalyst.

[0024] Comparative Example 1 The preparation of the foamed nickel composite catalyst does not involve the CVD step, and the remaining steps are the same as those in Example 1.

[0025] Comparative Example 2 In the preparation of the foamed nickel composite catalyst, the CVD atmosphere does not contain NH3, and the remaining steps are consistent with those in Example 1.

[0026] Comparative Example 3 In the preparation of the nickel foam composite catalyst, nickel nitrate was not added, and the remaining steps were consistent with those in Example 1.

[0027] Comparative Example 4 No cobalt nitrate was added during the preparation of the foamed nickel composite catalyst, and the remaining steps were the same as those in Example 1.

[0028] Comparative Example 5 No citric acid was added during the preparation of the nickel foam composite catalyst, and the remaining steps were the same as those in Example 1.

[0029] Test Example 1 Electrocatalytic hydrogen evolution performance test: The composite catalyst prepared in the examples and comparative examples was used as the working electrode, mercury oxide as the reference electrode, and platinum as the counter electrode. The electrochemical performance test was carried out using a Chenhua 760D electrochemical workstation in a 1 M KOH solution. At a current density of 500 mA / cm 2 The hydrogen evolution overpotential at is recorded in the following table.

[0030]

[0031] It can be seen from the data of the examples and comparative examples that the composite catalyst prepared in the present invention has good electrocatalytic hydrogen evolution activity.

[0032] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A foamed nickel composite catalyst, characterized in that: The foamed nickel composite catalyst comprises a foamed nickel substrate, a nitrogen-doped graphene carbon layer deposited on the foamed nickel substrate by CVD, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped carbon layer.

2. A method for preparing a foamed nickel composite catalyst as claimed in claim 1, characterized in that: The specific steps of the preparation method are as follows: S2-1: The nickel foam was ultrasonically cleaned with a 1 M hydrochloric acid solution for 10 to 20 minutes, and then ultrasonically cleaned with deionized water and anhydrous ethanol for 5 to 15 minutes, respectively. The nickel foam was then dried in a vacuum drying oven at 60°C for 12 to 16 hours to obtain a nickel foam substrate. S2-2: placing the nickel foam substrate in a CVD tube furnace, raising the temperature to 800-1000°C, introducing a NH3 / CH4 / H2 / Ar mixed gas, maintaining the temperature for 10-30 minutes, and then naturally cooling to room temperature to obtain a CVD-treated nickel foam; S2-3: Nickel nitrate and cobalt nitrate are mixed and dissolved in deionized water, citric acid is added, and ultrasonic treatment is performed for 30 to 60 minutes. The foamed nickel after CVD treatment is added and ultrasonic treatment is performed for 30 minutes. The sample is then vacuum dried at 80°C for 10 to 12 hours. The dried sample is heated to 500 to 600°C in an Ar / H2 mixed gas and kept warm for 2 hours to obtain the foamed nickel composite catalyst.

3. The method for preparing a foamed nickel composite catalyst according to claim 2, wherein: The porosity of the nickel foam in S2-1 is 90% to 95%.

4. The method for preparing a foamed nickel composite catalyst according to claim 2, wherein: The volume ratio of the NH3 / CH4 / H2 / Ar mixed gas in S2-2 is 1:5:20:

100.

5. The method for preparing a foamed nickel composite catalyst according to claim 2, wherein: The volume ratio of the Ar / H2 mixed gas in S2-3 is 9:

1.

6. The method for preparing a foamed nickel composite catalyst according to claim 2, wherein: In the S2-3, nickel nitrate and cobalt nitrate are mixed in a molar ratio of (1-3):

1.

7. The method for preparing a foamed nickel composite catalyst according to claim 2, wherein: Citric acid in an amount equimolar to nickel nitrate is added to S2-3.

8. Use of the foamed nickel composite catalyst according to claim 1, characterized in that: The foamed nickel composite catalyst can be applied to the field of hydrogen production by electrolysis of water.

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