A foamed nickel composite catalyst and its application in hydrogen production by electrolysis of water

Abstract

The present application relates to a kind of foamed nickel composite catalyst and its application in electrolytic water hydrogen production, belong to electrolytic water hydrogen production technical field.The composite catalyst is with foamed nickel as three-dimensional conductive framework, removes surface oxide layer and impurity by hierarchical pretreatment, grows nitrogen-doped graphene layer on the surface of foamed nickel by chemical vapor deposition method, and then loads superfine nickel-cobalt alloy nanoparticles between graphene layer by citric acid complexation-hydrogen reduction method.The catalyst is doped by nitrogen atom to optimize graphene electronic structure, combined with the d-band center matching effect of nickel-cobalt alloy, significantly improves hydrogen adsorption / desorption kinetics performance;The steric hindrance effect of citric acid realizes metal particle nanocrystallization, and inhibits agglomeration;Double conductive network design makes electron mobility significantly improve.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis hydrogen production technology, and relates to a foamed nickel composite catalyst and its application in water electrolysis hydrogen production. Background Technology

[0002] As a core component of the hydrogen energy industry chain, the large-scale commercial application of water electrolysis for hydrogen production is still limited by the overall performance bottleneck of catalysts. Firstly, while noble 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 scarcity leads to high costs, making it difficult to support the sustainable development of the hydrogen economy. Secondly, although non-noble metal catalysts offer significantly lower costs, they suffer from rapid activity decay, poor conductivity, and insufficient stability, hindering their industrial application.

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

[0004] This invention provides a foamed nickel composite catalyst and its application in water electrolysis for hydrogen production, exhibiting excellent electrocatalytic activity.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A nickel foam composite catalyst, comprising a nickel foam substrate, a nitrogen-doped graphene carbon layer CVD deposited on the nickel foam substrate, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped graphene carbon layer.

[0007] A method for preparing a nickel foam composite catalyst, the specific steps of which are as follows:

[0008] S2-1: The nickel foam was ultrasonically cleaned with 1 M hydrochloric acid solution for 10-20 min, then ultrasonically cleaned with deionized water and anhydrous ethanol for 5-15 min respectively, and then dried in a vacuum drying oven at 60 ℃ for 12-16 h to obtain the nickel foam substrate.

[0009] S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 800-1000 ℃, introduce a mixed gas of NH3 / CH4 / H2 / Ar, keep it at the temperature for 10-30 min, and then cool it naturally to room temperature to obtain CVD-treated nickel foam.

[0010] S2-3: Mix nickel nitrate and cobalt nitrate and dissolve them in deionized water. Add citric acid and sonicate for 30-60 min. Add CVD-treated nickel foam and sonicate for 30 min. Then, vacuum dry at 80 °C for 10-12 h. Heat the dried sample to 500-600 °C in an Ar / H2 mixed gas and keep it at that temperature for 2 h to obtain the nickel foam composite catalyst.

[0011] Furthermore, the porosity of the nickel foam in S2-1 is 90% to 95%.

[0012] Furthermore, the volume ratio of the NH3 / CH4 / H2 / Ar mixed gas in S2-2 is 1:5:25:100.

[0013] Furthermore, the volume ratio of the Ar / H2 mixed gas in S2-3 is 9:1.

[0014] Furthermore, in S2-3, nickel nitrate and cobalt nitrate are mixed in a molar ratio of (1-3):1.

[0015] Furthermore, citric acid in an equimolar amount of nickel nitrate is added to S2-3.

[0016] An application of a foamed nickel composite catalyst, which can be used in the field of hydrogen production by water electrolysis.

[0017] The nickel foam substrate provides a three-dimensional conductive framework, ensuring the catalyst's mechanical stability and high specific surface area. Pretreatment steps with hydrochloric acid, deionized water, and ethanol effectively remove surface oxides and other impurities, while deionized water washing prevents residual Cl... - The rapid volatility of anhydrous ethanol can prevent localized agglomeration of carbon layers caused by water residue, thus enhancing the catalytic poisoning effect on subsequent CVD processes.

[0018] Subsequently, in the synthesis of nitrogen-doped graphene carbon layers, NH3, as the nitrogen source, decomposes into active nitrogen atoms at 800–1000 °C. The carbon atoms generated from the cracking of CH4 are deposited on the surface of nickel foam to form a graphene lattice. Nitrogen atoms are incorporated into the six-membered rings of graphene through substitution doping. The H2 / Ar mixed gas not only acts as a reducing atmosphere to suppress the oxidation of nickel foam but also controls the defect density of the carbon layer by adjusting the H2 ratio. An appropriate amount of H2 can etch amorphous carbon, exposing more active sites at the graphene edges, while Ar acts as a carrier gas to ensure the uniformity of the reaction atmosphere, ultimately generating a nitrogen-doped graphene layer. The electronegativity of nitrogen atoms is higher than that of carbon, causing positive charge accumulation among adjacent carbon atoms and enhancing the adsorption capacity for reaction intermediates. With a fixed amount of nitrogen doping, the conductivity of the carbon layer can be increased, forming a vertical conductive network with the nickel foam, improving electron mobility and reducing interfacial resistance. Nitrogen atoms can also act as Lewis base sites, increasing the density of active sites on the catalyst.

[0019] When nickel-cobalt composite nanoparticles are generated in situ on the surface of graphene carbon layers, nickel nitrate / cobalt nitrate form a stable complex under the action of citric acid. The cavitation effect generated by ultrasonic treatment promotes the penetration of the complex into the graphene interlayer. Citric acid restricts crystal nucleus growth 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, this invention effectively reduces the cost of the catalyst for hydrogen production by electrolysis of water by replacing traditional noble metal catalysts such as Pt and Pd with a Ni / Co non-noble metal system.

[0020] The beneficial effects of this invention are:

[0021] This invention uses nickel foam as the substrate material. During the CVD process, a mixed gas of NH3 / CH4 / H2 / Ar is introduced to deposit a nitrogen-doped graphene layer on the surface of the nickel foam. The electronic structure of the graphene is optimized by nitrogen atom substitution doping, and the defect density is controlled by H2 etching to expose high-density active edge sites. Subsequently, Ni is uniformly dispersed between the graphene layers by utilizing the strong coordination between citric acid and metal ions. 2+ / Co 2+ NiCo composite nanoparticles were prepared by H2 reduction, and the metal-carbon interfacial bonding was enhanced by pyrolysis carbonization of citric acid. The electronic structure regulation of the nickel-cobalt composite nanoparticles significantly reduced the hydrogen evolution overpotential of the catalyst in alkaline medium. Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0023] Example 1

[0024] A nickel foam composite catalyst, comprising a nickel foam substrate, a nitrogen-doped graphene carbon layer CVD deposited on the nickel foam substrate, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped graphene carbon layer.

[0025] A method for preparing a nickel foam composite catalyst, the specific steps of which are as follows:

[0026] S2-1: The foamed nickel with a porosity of 93% was ultrasonically cleaned for 15 min with 1 M hydrochloric acid solution, and then ultrasonically cleaned for 10 min with deionized water and anhydrous ethanol respectively. Finally, it was dried in a vacuum drying oven at 60 ℃ for 14 h to obtain the foamed nickel substrate.

[0027] S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 900 ℃, introduce a mixed gas of NH3 / CH4 / H2 / Ar with a volume ratio of 1:5:25:100, hold it at that temperature for 20 min, and then cool it naturally to room temperature to obtain the CVD-treated nickel foam.

[0028] S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 2:1 and dissolved in deionized water. Citric acid with an equimolar amount of nickel nitrate was added, and the mixture was sonicated for 45 min. CVD-treated nickel foam was added, and the mixture was sonicated for 30 min. Subsequently, the mixture was vacuum dried at 80 °C for 11 h. The dried sample was then heated to 550 °C in an Ar / H2 mixed gas with a volume ratio of 9:1 and held at this temperature for 2 h to obtain the nickel foam composite catalyst.

[0029] Example 2

[0030] A nickel foam composite catalyst, comprising a nickel foam substrate, a nitrogen-doped graphene carbon layer CVD deposited on the nickel foam substrate, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped graphene carbon layer.

[0031] A method for preparing a nickel foam composite catalyst, the specific steps of which are as follows:

[0032] S2-1: The foamed nickel with a porosity of 90% was ultrasonically cleaned for 10 min with 1 M hydrochloric acid solution, and then ultrasonically cleaned for 5 min with deionized water and anhydrous ethanol respectively. Finally, it was dried in a vacuum drying oven at 60 ℃ for 12 h to obtain the foamed nickel substrate.

[0033] S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 800 ℃, and introduce a mixed gas of NH3 / CH4 / H2 / Ar with a volume ratio of 1:5:25:100. Hold the temperature for 10 min, and then cool it naturally to room temperature to obtain the CVD-treated nickel foam.

[0034] S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 1:1 and dissolved in deionized water. Citric acid with an equimolar amount of nickel nitrate was added, and the mixture was sonicated for 30 min. CVD-treated nickel foam was added, and the mixture was sonicated for 30 min. Subsequently, the mixture was vacuum dried at 80 °C for 10 h. The dried sample was then heated to 500 °C in an Ar / H2 mixed gas with a volume ratio of 9:1 and kept at this temperature for 2 h to obtain the nickel foam composite catalyst.

[0035] Example 3

[0036] A nickel foam composite catalyst, comprising a nickel foam substrate, a nitrogen-doped graphene carbon layer CVD deposited on the nickel foam substrate, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped graphene carbon layer.

[0037] A method for preparing a nickel foam composite catalyst, the specific steps of which are as follows:

[0038] S2-1: The foamed nickel with a porosity of 95% was ultrasonically cleaned for 20 min with 1 M hydrochloric acid solution, and then ultrasonically cleaned for 15 min with deionized water and anhydrous ethanol respectively. Finally, it was dried in a vacuum drying oven at 60 ℃ for 16 h to obtain the foamed nickel substrate.

[0039] S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 1000 ℃, introduce a mixed gas of NH3 / CH4 / H2 / Ar with a volume ratio of 1:5:25:100, hold it at that temperature for 30 min, and then cool it naturally to room temperature to obtain the CVD-treated nickel foam.

[0040] S2-3: Nickel nitrate and cobalt nitrate were mixed in a molar ratio of 3:1 and dissolved in deionized water. Citric acid with an equimolar amount of nickel nitrate was added, and the mixture was sonicated for 60 min. CVD-treated nickel foam was added, and the mixture was sonicated for 30 min. Subsequently, the mixture was vacuum dried at 80 °C for 12 h. The dried sample was then heated to 600 °C in an Ar / H2 mixed gas with a volume ratio of 9:1 and held at this temperature for 2 h to obtain the nickel foam composite catalyst.

[0041] Comparative Example 1

[0042] The preparation of the nickel foam composite catalyst does not involve a CVD step; the remaining steps are the same as in Example 1.

[0043] Comparative Example 2

[0044] The CVD atmosphere in the preparation of the nickel foam composite catalyst does not contain NH3, and the remaining steps are the same as in Example 1.

[0045] Comparative Example 3

[0046] Nickel nitrate was not added in the preparation of the foamed nickel composite catalyst, and the remaining steps were the same as in Example 1.

[0047] Comparative Example 4

[0048] Cobalt nitrate was not added in the preparation of the nickel foam composite catalyst, and the remaining steps were the same as in Example 1.

[0049] Comparative Example 5

[0050] Citric acid was not added in the preparation of the nickel foam composite catalyst, and the remaining steps were the same as in Example 1.

[0051] Test Example 1

[0052] Electrocatalytic hydrogen evolution performance test:

[0053] The composite catalysts prepared in the examples and comparative examples were used as working electrodes, mercury oxide was used as a reference electrode, and a platinum sheet was used as a counter electrode. Electrochemical performance tests were conducted using a Chenhua 760D electrochemical workstation in a 1 M KOH solution. The current density was 500 mA / cm². 2 The hydrogen evolution overpotential at the point is recorded in the table below.

[0054] Example 1 234 Example 2 226 Example 3 220 Comparative Example 1 331 Comparative Example 2 248 Comparative Example 3 281 Comparative Example 4 274 Comparative Example 5 305

[0055] As can be seen from the examples and comparative data, the composite catalyst prepared by the present invention has good electrocatalytic hydrogen evolution activity.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention are within the scope of the present invention.

Claims

1. A foamed nickel composite catalyst, characterized in that, The nickel foam composite catalyst comprises a nickel foam substrate, a nitrogen-doped graphene carbon layer deposited by CVD on the nickel foam substrate, and nickel-cobalt composite nanoparticles supported on the nitrogen-doped graphene carbon layer. The specific steps of the preparation method of the nickel foam composite catalyst are as follows: S2-1: The nickel foam was ultrasonically cleaned with 1 M hydrochloric acid solution for 10-20 min, then ultrasonically cleaned with deionized water and anhydrous ethanol for 5-15 min respectively, and then dried in a vacuum drying oven at 60 ℃ for 12-16 h to obtain the nickel foam substrate. S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 800-1000 ℃, introduce a mixed gas of NH3 / CH4 / H2 / Ar, keep it at the temperature for 10-30 min, and then cool it naturally to room temperature to obtain CVD-treated nickel foam. S2-3: Mix nickel nitrate and cobalt nitrate and dissolve them in deionized water. Add citric acid and sonicate for 30-60 min. Add CVD-treated nickel foam and sonicate for 30 min. Then, vacuum dry at 80 °C for 10-12 h. Heat the dried sample to 500-600 °C in an Ar / H2 mixed gas and keep it at that temperature for 2 h to obtain the nickel foam composite catalyst.

2. A method for preparing the foamed nickel composite catalyst as described 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 1 M hydrochloric acid solution for 10-20 min, then ultrasonically cleaned with deionized water and anhydrous ethanol for 5-15 min respectively, and then dried in a vacuum drying oven at 60 ℃ for 12-16 h to obtain the nickel foam substrate. S2-2: Place the nickel foam substrate in a CVD tube furnace, heat it to 800-1000 ℃, introduce a mixed gas of NH3 / CH4 / H2 / Ar, keep it at the temperature for 10-30 min, and then cool it naturally to room temperature to obtain CVD-treated nickel foam. S2-3: Mix nickel nitrate and cobalt nitrate and dissolve them in deionized water. Add citric acid and sonicate for 30-60 min. Add CVD-treated nickel foam and sonicate for 30 min. Then, vacuum dry at 80 °C for 10-12 h. Heat the dried sample to 500-600 °C in an Ar / H2 mixed gas and keep it at that temperature for 2 h to obtain the nickel foam composite catalyst.

3. The method for preparing a foamed nickel composite catalyst according to claim 2, characterized in that, 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, characterized in that, The volume ratio of the NH3 / CH4 / H2 / Ar mixed gas in S2-2 is 1:5:25:

100.

5. The method for preparing a foamed nickel composite catalyst according to claim 2, characterized in that, 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, characterized in that, In 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, characterized in that, Citric acid, in an equimolar amount of nickel nitrate, is added to S2-3.

8. The application of the foamed nickel composite catalyst as described in claim 1, characterized in that, The foamed nickel composite catalyst is used for hydrogen production via water electrolysis.