Nickel-molybdenum-based electrolyzed water catalytic electrode material, preparation method and application of nickel-molybdenum-based electrolyzed water catalytic electrode material

Abstract

The invention provides a method for preparing a nickel-molybdenum-sulfur / nickel-molybdenum catalytic electrode through an in-situ etching method and application of the nickel-molybdenum-sulfur / nickel-molybdenum catalytic electrode, and belongs to the technical direction of new material preparation in the field of hydrogen energy. Comprising the key steps that a nickel-molybdenum alloy base material is soaked in a mixed solution containing sodium persulfide and ammonium sulfate for a reaction, the nickel-molybdenum alloy base material is taken out and cleaned with deionized water after being statically soaked for a certain time, and the nickel-molybdenum alloy base material is self-dried in air. In the preparation process, the electrode can be prepared through one-step reaction, and the operation is simple; sodium persulfide and ammonium sulfate which are safe, environmentally friendly and low in cost are used as etching agents in the process; the preparation method is mild in condition, does not need a high-temperature and high-pressure environment, can be completed only by immersing the base material into a reaction solution, and is beneficial to large-area production. The obtained nickel-molybdenum-sulfur-based self-supporting electrode shows relatively high electrochemical activity and stability, the overpotential of a catalytic reaction can be remarkably reduced, the working voltage and the overall energy consumption of an electrolytic cell are further reduced, and the nickel-molybdenum-sulfur-based self-supporting electrode has good industrial application potential.

Description

Technical Field

[0001] This invention belongs to the technical field of electrode materials for hydrogen production by water electrolysis, specifically relating to a nickel-molybdenum-based catalytic electrode material for water electrolysis, its preparation method, and its application. Background Technology

[0002] Currently, global energy supply remains highly dependent on fossil fuels, accounting for over 80%. Accelerating the development of renewable energy and promoting the transformation of the energy system towards a green and sustainable direction has become a major national strategy. However, renewable energy sources such as solar and wind power are intermittent and volatile, making direct and stable grid connection difficult, resulting in low actual utilization rates. Among various electrochemical energy storage technologies, water electrolysis for hydrogen production can achieve large-scale consumption of renewable energy, becoming an important path to improve the utilization rate of renewable energy. With the advancement of technologies such as wind power and photovoltaic power generation, and the continuous decline in electricity costs, coupled with the continuous optimization of water electrolysis for hydrogen production technology and the gradual reduction in energy consumption, the cost of renewable energy-driven water electrolysis for hydrogen production is expected to approach the level of traditional fossil fuel reforming for hydrogen production, thus possessing market competitiveness. Electrocatalytic water electrolysis for hydrogen production, as a highly efficient and clean hydrogen production method, is considered one of the key technologies for addressing global energy challenges and reducing carbon emissions. Developing large-scale, high-efficiency, and long-life water electrolysis for hydrogen production equipment is of significant strategic importance for promoting the progress of the hydrogen energy industry.

[0003] The high energy consumption and cost of current water electrolysis hydrogen production technology limit its large-scale industrial application. One key path to improving water electrolysis efficiency is the development of highly active hydrogen evolution and oxygen evolution catalysts. While iridium dioxide and ruthenium dioxide exhibit excellent catalytic activity in the oxygen evolution reaction, their corresponding metal elements are scarce in the Earth's crust and expensive, making their widespread use in commercial water electrolysis systems difficult. Therefore, developing low-cost, easily prepared, and highly catalytically active water electrolysis electrode materials is of significant practical importance.

[0004] Currently, coating powdered catalysts onto conductive substrates typically faces two main challenges: firstly, the coating increases interfacial resistance, limiting the improvement of electrocatalytic performance; secondly, insufficient adhesion between the catalyst and the substrate results in limited exposure of active sites. Furthermore, the binder may degrade due to environmental factors, triggering unpredictable side reactions. In contrast, self-supporting electrocatalysts effectively circumvent these inherent defects of powdered catalysts. Traditional solvothermal methods for preparing self-supporting catalysts often involve multiple chemical reagents, complex processes, and low reliability, and typically require a high-temperature, high-pressure, and closed environment.

[0005] Nickel-molybdenum-based water electrolysis catalysts exhibit highly efficient hydrogen evolution and oxygen evolution catalysis in alkaline electrolytes, making them one of the most promising industrial-grade non-precious metal alkaline water electrolysis catalysts. Traditional water splitting technologies typically require the separate preparation of two single-functional catalysts for anolyte oxygen evolution and catholyte hydrogen evolution, leading to a significant increase in development costs. Therefore, developing catalytic materials with dual hydrogen and oxygen evolution activities to achieve full / composite water splitting driven by a single catalyst offers significant advantages. This design simplifies electrode fabrication processes, avoids mutual interference between different catalysts during operation, effectively reduces reaction potential, and improves hydrogen production efficiency and system operational stability. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention proposes a self-supporting nickel-molybdenum-based catalytic electrode material for water electrolysis, its preparation method, and its applications. The prepared material is based on a nickel-molybdenum alloy substrate and composited with nickel-molybdenum-sulfur nanosheets. It can serve as a highly efficient bifunctional catalyst in non-acidic media for catalyzing the hydrogen evolution reaction and oxygen evolution reaction in water electrolysis.

[0007] The technical solution adopted in this invention is as follows:

[0008] The present invention provides a nickel-molybdenum-based catalytic electrode material for water electrolysis, comprising a nickel-molybdenum alloy as a substrate, wherein the surface of the foamed nickel-molybdenum alloy is covered with two-dimensional layered nickel-molybdenum-sulfur-based honeycomb nanosheets.

[0009] Furthermore, the present invention provides a preparation method for fabricating a self-supporting electrolytic water electrolysis catalytic electrode material as described in the first aspect above. The method involves first pre-treating and cleaning a foamed nickel-molybdenum alloy material, then immersing the treated nickel-molybdenum alloy material in an aqueous solution containing sodium persulfate and ammonium sulfate for etching, followed by cleaning and drying under natural conditions to form a nickel-molybdenum-sulfur / nickel-molybdenum alloy material.

[0010] Furthermore, the concentrations of sodium persulfide and ammonium sulfate in the etching aqueous solution are 0.01-1 mol / L.

[0011] Furthermore, the ammonium sulfate may be replaced by sodium sulfate or potassium sulfate, but ammonium sulfate is preferred.

[0012] Furthermore, the nickel-molybdenum alloy used as the substrate is one or more of nickel-molybdenum alloy powder, nickel-molybdenum alloy sheet, nickel-molybdenum alloy plate, nickel-molybdenum alloy foil, and foamed nickel-molybdenum alloy, preferably foamed nickel-molybdenum alloy.

[0013] Furthermore, the nickel-molybdenum alloy is immersed in an aqueous solution of sodium persulfate and ammonium sulfate for 1-48 hours, preferably 24 hours.

[0014] The specific steps are as follows:

[0015] First, the nickel-molybdenum alloy with a nickel-molybdenum ratio of 1:1 is immersed in hydrochloric acid solution for ultrasonic cleaning, and then ultrasonically cleaned in acetone.

[0016] Then, after the cleaned nickel-molybdenum alloy is dried, it is immersed in an aqueous solution containing sodium sulfide and ammonium sulfate, taken out and washed with deionized water, and then dried in a natural environment.

[0017] This invention proposes that the nickel-molybdenum-sulfur-based nanosheet / nickel-molybdenum alloy composite electrode material prepared by the above preparation method can form different composite materials with different surface compositions and structures by adjusting the ion ratio and immersion time of the etching solution, and these composite materials can be used as positive and negative electrode materials in water electrolysis.

[0018] The beneficial effects of this invention are as follows:

[0019] 1. This invention uses foamed nickel-molybdenum alloy as a current collector and catalytically active precursor. Fresh crystal nuclei are generated on its surface through a one-step oxidation etching method, and layered nickel-molybdenum-sulfur-based nanosheets are grown in situ.

[0020] 2. The electrode material prepared by this invention has abundant nanosheet structures distributed on its surface, which not only have a high specific surface area but also can be tightly bonded to the conductive substrate. This structure also has excellent conductivity and mechanical stability, and can maintain high catalytic activity and long-term operational stability even when operating at industrial-grade high current densities.

[0021] 3. The preparation process of the present invention is simple to operate, the reaction conditions are mild, the raw material cost is low and there is no pollutant emission, making it suitable for large-scale production.

[0022] 4. In the application of this invention, the morphology and structure of nickel-molybdenum-sulfur compounds on the material surface can be changed by adjusting the immersion time and etching solution concentration, thereby optimizing the adaptability for the actual working conditions of the cathode or anode and improving the corresponding electrolytic gas production efficiency. Attached Figure Description

[0023] Figure 1 (a) is a scanning electron microscope image of the nickel-molybdenum foam used in the embodiments of the present invention. Figure 1 (b) The prepared nickel-molybdenum-sulfur / nickel-molybdenum-24 (NiMoS) x Scanning electron microscope image of / NiMo-24);

[0024] Figure 2 These are linear sweep voltammetric curves of the oxygen evolution reaction of several materials prepared in the embodiments of this invention;

[0025] Figure 3 These are linear sweep voltammetry curves of the hydrogen evolution reaction of several materials prepared in the embodiments of this invention;

[0026] Figure 4The nickel-molybdenum-sulfur / nickel-molybdenum-24 (NiMoS) prepared in the embodiments of the present invention x Oxygen evolution reaction durability test curve of / NiMo-24);

[0027] Figure 5 The nickel-molybdenum-sulfur / nickel-molybdenum-24 (NiMoS) prepared in the embodiments of the present invention x The hydrogen evolution reaction durability test curve of / NiMo-24). Detailed Implementation

[0028] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0029] To clearly illustrate the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions involved in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the embodiments described below are only some examples and not all implementation methods. Therefore, the detailed description of the embodiments shown in the accompanying drawings does not constitute a limitation on the scope of protection of this application, but is only used to illustrate some implementation methods of this application. Based on these embodiments, all other implementation methods obtained by those skilled in the art without creative effort fall within the scope of protection of this application.

[0030] Example 1:

[0031] This embodiment discloses a nickel-molybdenum-based catalytic electrode material for water electrolysis, which is used as an electrode material for water electrolysis. Specifically, it includes a foamed nickel-molybdenum alloy as a substrate, and nickel-molybdenum-sulfur-based nanosheet structures grown in situ on the surface of the foamed nickel-molybdenum alloy.

[0032] The nickel-molybdenum alloy described in this application can be selected from one or more forms such as powder, sheet, plate, foil, or foam. In this embodiment, a foamed nickel-molybdenum alloy is selected as the substrate, which benefits from its high specific surface area, facilitating the natural growth of nanostructures during subsequent immersion. It should be noted that other forms of nickel-molybdenum alloy materials can achieve similar effects under the concept of this application and should be considered as equivalent alternatives, falling within the scope of protection of this application.

[0033] Regarding the manufacturing method of the nickel-molybdenum-sulfur / nickel-molybdenum alloy material in the above embodiments, the preferred conditions include:

[0034] (1) The concentrations of sodium persulfate and ammonium sulfate in the etching solution are 0.2 mol / L;

[0035] (2) The nickel-molybdenum alloy was immersed in the etching solution for 24 hours.

[0036] To address the above conditions, several implementation schemes are provided for explanation.

[0037] Implementation Plan 1

[0038] A nickel-molybdenum-sulfur nanosheet / foamed nickel-molybdenum composite material is prepared by the following method:

[0039] A nickel-molybdenum foam with a nickel-molybdenum mass ratio of 1:1 and an area of ​​1cm×3cm was immersed in a 1mol / L hydrochloric acid aqueous solution and ultrasonically cleaned for 15 minutes. After removal, the surface was cleaned with deionized water to remove any remaining acid solution. Subsequently, the foam was ultrasonically cleaned in an acetone solution for 15 minutes. After removal, the surface was cleaned with deionized water to remove any remaining acetone, thus obtaining the treated nickel-molybdenum foam alloy.

[0040] 2 mmol sodium sulfate and 2 mmol sulfur powder were added to 10 mL of deionized water and ultrasonically dispersed. The mixture was then stirred until homogeneous to obtain a yellow transparent sodium persulfate aqueous solution. Finally, 2 mmol ammonium sulfate was added to the sodium persulfate aqueous solution and stirred until homogeneous to obtain the etching solution.

[0041] The foamed nickel-molybdenum alloy obtained in the previous step was immersed in a prepared aqueous solution containing sodium persulfide and ammonium sulfate, and reacted for 24 hours each. After the reaction, it was washed with deionized water and air-dried to obtain a self-supported catalytic electrode with nickel-molybdenum-sulfur nanosheets grown on the nickel-molybdenum alloy, namely nickel-molybdenum-sulfur / nickel-molybdenum-24 (NiMoS2). x / NiMo-24).

[0042] Electron scanning microscope images of the catalytic electrode surface prepared in this scheme, such as Figure 1 As shown. Figure 1 (a) is a scanning electron microscope image of the untreated nickel-molybdenum foam surface, showing a relatively flat metal nanoparticle structure. Figure 1 (b) is a scanning electron microscope image of the surface of the nickel-molybdenum foam after etching, showing a relatively abundant honeycomb nanosheet structure with a thickness of approximately 10 nm. This structure has a large specific surface area and abundant electrochemical active sites, while the abundant pore structure is conducive to improving the transport efficiency of materials and electrons, thereby enhancing the electrochemical performance of the catalyst.

[0043] Implementation Plan 2

[0044] The foamed nickel-molybdenum mixture with a mass ratio of 1:1 according to Implementation Scheme 1 was ultrasonically cleaned in hydrochloric acid solution and acetone for 15 minutes, and then air-dried naturally. The resulting sample was denoted as nickel-molybdenum.

[0045] Implementation Plan 3

[0046] Materials and parameters

[0047] The foamed nickel-molybdenum alloy (Ni:Mo = 1:1, porosity 85%) was cut into strips of 1cm × 3cm; the etching solution was a solution prepared by 2 mmol sodium sulfate, 2 mmol sulfur powder, 2 mmol ammonium sulfate and 10 mL water; the cleaning reagents were deionized water (resistivity ≥ 18.2 MΩ·cm) and analytical grade acetone.

[0048] First, pretreatment is performed by immersing the foamed nickel-molybdenum alloy sequentially in 1 mol / L hydrochloric acid solution and acetone, and ultrasonically cleaning for 15 minutes each (ultrasonic power 100W, frequency 40kHz) to remove the surface oxide layer and oil stains. Then, the surface is rinsed with deionized water to remove any residual solution and dried.

[0049] The dried alloy was vertically immersed in the etching solution and left to stand at room temperature (25°C) for 12 hours.

[0050] Remove the alloy, rinse thoroughly with deionized water to remove any residual solvent, and then air dry naturally (ambient humidity ≤50%, temperature 25℃). The resulting sample is nickel-molybdenum-sulfur / nickel-molybdenum-12 (NiMoS). x / NiMo-12).

[0051] Implementation Plan 4

[0052] First, pretreatment is performed by immersing the foamed nickel-molybdenum alloy sequentially in 1 mol / L hydrochloric acid solution and acetone, and ultrasonically cleaning for 15 minutes each (ultrasonic power 100W, frequency 40kHz) to remove the surface oxide layer and oil stains. Then, the surface is rinsed with deionized water to remove any residual solution and dried.

[0053] The dried alloy was vertically immersed in the etching solution and left to stand at room temperature (25°C) for 36 hours.

[0054] Remove the alloy, rinse thoroughly with deionized water to remove any residual solvent, and then air dry naturally (ambient humidity ≤50%, temperature 25℃). The resulting sample is nickel-molybdenum-sulfur / nickel-molybdenum-36 (NiMoS). x / NiMo-36).

[0056] Comparative Example 1: 5 mg of commercial ruthenium dioxide catalyst, 900 μL of isopropanol, 50 μL of deionized water and 50 μL of 0.5% Nafion solution were mixed and ultrasonically dispersed for 30 minutes. The resulting mixture was then dropped onto the surface of a glassy carbon electrode and allowed to dry naturally to obtain the ruthenium dioxide electrode material.

[0057] Comparative Example 2: 5 mg of commercial platinum-carbon catalyst, 900 μL of isopropanol, 50 μL of deionized water and 50 μL of 0.5% Nafion solution were mixed and ultrasonically dispersed for 30 minutes. The resulting mixture was then dropped onto the surface of a glassy carbon electrode and allowed to dry naturally to obtain the platinum-carbon catalytic electrode material.

[0058] Performance testing:

[0059] The nickel-molybdenum-sulfur / nickel-molybdenum electrode prepared in Scheme 1, Scheme 2, Scheme 3, Scheme 4, and Comparative Example 1 ruthenium dioxide electrode were used as working electrodes, respectively, and paired with a graphite rod counter electrode and a mercury / mercury oxide reference electrode to construct a three-electrode system in 1 mol / L potassium hydroxide electrolyte. The oxygen evolution and hydrogen evolution performance of the catalytic electrodes were tested using linear sweep voltammetry at a scan rate of 5 mV / s. The linear sweep voltammetric curves for the oxygen evolution and hydrogen evolution reactions are shown in [the table / image / image]. Figure 2 and Figure 3 middle.

[0060] Depend on Figure 2 It can be known that at 500mA / cm 2 Nickel-molybdenum sulfide / nickel-molybdenum NiMoS was prepared using nickel foam (Ni), ruthenium oxide (RuO2), and nickel-molybdenum foam (NiMo) at a current density. x / NiMo-12, NiMoS x / NiMo-24, NiMoS x The overpotentials corresponding to the NiMo-36 electrode are 740mV, 680mV, 610mV, 410mV, 280mV, and 450mV, respectively, indicating that NiMoS x / NiMo-24 exhibits the best oxygen evolution reaction catalytic performance and is significantly superior to commercial RuO2 and untreated foamed NiMo alloys.

[0061] Depend on Figure 3 It can be seen that at 100mA / cm 2 Nickel-molybdenum sulfide / nickel-molybdenum NiMoS was prepared using nickel foam (Ni), ruthenium oxide (RuO2), and nickel-molybdenum foam (NiMo) at a current density. x / NiMo-12, NiMoS x / NiMo-24, NiMoS x The overpotentials corresponding to the NiMo-36 electrode are 431mV, 339mV, 296mV, 189mV, 121mV, and 138mV, respectively, indicating that NiMoS x / NiMo-24 exhibits the best oxygen evolution reaction catalytic performance and is significantly superior to commercial Pt / C and untreated foamed NiMo alloys.

[0062] Using the nickel-molybdenum-sulfur / nickel-molybdenum electrode prepared in Implementation Scheme 1 as the working electrode, a graphite rod as the counter electrode, and a mercury / mercury oxide electrode as the reference electrode, the stability of the oxygen evolution reaction and hydrogen evolution reaction of the nickel-molybdenum-sulfur / nickel-molybdenum electrode was tested in a three-electrode system.

[0063] Figure 4 and Figure 5 The prepared nickel-molybdenum-sulfur / nickel-molybdenum electrodes were demonstrated at approximately 500 mA / cm². 2 Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) time-current curves at current density. The results show that the current density of the electrode did not decrease significantly after long-term testing, indicating that it has excellent long-term OER and HER stability and demonstrates its potential for application under high-current conditions in industrial applications.

[0064] This invention is not limited to the embodiments listed above. Any reasonable improvements or modifications made based on the inventive concept should be included within the scope of protection of this invention. The specific embodiments are merely examples provided for ease of understanding and should not be considered as limitations on the scope of protection. The actual scope of protection of this invention should be determined by the claims, and the content of the specification can be used to interpret the claims.

Claims

1. A nickel-molybdenum-based catalytic electrode material for water electrolysis, characterized in that: It includes a nickel-molybdenum alloy as a substrate, the surface of which is covered with a two-dimensional layered nickel-molybdenum-sulfur nanosheet structure.

2. A preparation method, characterized in that, The method for preparing the nickel-molybdenum-based electrolytic water catalytic electrode material according to claim 1 includes the following steps: first, the nickel-molybdenum alloy substrate is pretreated by cleaning, and then it is immersed in an etching aqueous solution containing sodium persulfate and ammonium sulfate to carry out a chemical etching reaction; after etching, the product is cleaned with deionized water and naturally dried at room temperature to finally obtain a composite electrode material with nickel-molybdenum-sulfur nanosheets grown on the surface of the nickel-molybdenum alloy.

3. The preparation method according to claim 2, characterized in that: The concentration of the sodium persulfide aqueous solution is 0.01-1 mol / L.

4. The preparation method according to claim 2, characterized in that: The sodium persulfide aqueous solution is prepared by adding equal molar amounts of sodium sulfide and sulfur powder to deionized water, followed by ultrasonic dispersion and stirring.

5. The preparation method according to claim 2, characterized in that: The concentration of the ammonium sulfate aqueous solution is 0.01-1 mol / L.

6. The preparation method according to claim 2, characterized in that: The ammonium sulfate aqueous solution can be replaced by sodium sulfate or potassium sulfate aqueous solution.

7. The preparation method according to claim 2, characterized in that: The nickel-molybdenum alloy used as the substrate is one or more of nickel-molybdenum alloy powder, nickel-molybdenum alloy sheet, nickel-molybdenum alloy plate, nickel-molybdenum alloy foil, and foamed nickel-molybdenum alloy, preferably foamed nickel-molybdenum alloy. The nickel-molybdenum alloy is immersed in an aqueous solution of sodium sulfide and ammonium sulfate for 1-48 hours.

8. The preparation method according to claim 2, characterized in that: The specific steps are as follows: First, a nickel-molybdenum alloy with a nickel-molybdenum ratio of 1:1 is immersed in a hydrochloric acid solution for ultrasonic cleaning, followed by removal of residual acid from the surface with deionized water. Then, it is placed in acetone for further ultrasonic treatment, and after treatment, residual acetone is washed off with deionized water. Once the alloy sheet has air-dried, it is immersed in an aqueous solution containing sodium persulfate and ammonium sulfate for a specified time. After removal, it is rinsed with deionized water and air-dried at room temperature.

9. An application, characterized in that: The nickel-molybdenum-sulfur nanosheet / nickel-molybdenum alloy composite electrode material prepared by the method of claim 2 can be used to form different composite materials with different surface compositions and structures by adjusting the ion ratio and immersion time of the etching aqueous solution. These composite materials can then be used as positive and negative electrode materials in water electrolysis.

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