Lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrodes, their preparation methods, and applications.

Abstract

This invention provides a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, comprising a foamed metal substrate, a phosphide layer on the surface of the foamed metal substrate, and a NiMoCuLa layer on the surface of the phosphide layer. The phosphide is obtained by phosphating the foamed metal substrate, and NiMoCuLa is a Cu and La co-doped NiMo material. Phosphating treatment can alter the surface morphology and conductivity of the substrate material, increase the loading sites on the substrate surface, thereby increasing the active sites of the NiMoCuLa material, enhancing the bonding strength between the nickel-molybdenum-lanthanum-copper and the substrate, promoting electron transfer and shortening the electron transport channel, and improving its electrocatalytic hydrogen evolution activity. Therefore, this electrode has advantages such as low hydrogen evolution overpotential, good conductivity, high electrochemical stability and catalytic activity, long service life, and low cost, and has considerable application prospects in the field of water electrolysis.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis, specifically relating to a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, its preparation method, and its application. Background Technology

[0002] The rapid depletion of energy resources and increasing environmental pressures necessitate the exploration of sustainable clean energy sources to replace traditional fossil fuels. Hydrogen, due to its high energy density and environmentally friendly properties, is widely considered a promising sustainable energy carrier for addressing these two issues. An ideal sustainable hydrogen production method utilizes electricity generated from clean energy sources (such as solar cells) to drive the water splitting reaction, and highly efficient hydrogen evolution reaction (HER) electrocatalysts are essential for achieving high energy utilization efficiency. The key to water electrolysis for hydrogen production lies in the development of low overpotential and durable electrocatalysts. Existing highly efficient catalysts are mainly Pt-based and Ru-based, but their high cost limits their large-scale application.

[0003] More and more efficient catalysts are being developed and designed, but most catalysts are usually studied under laboratory conditions. In order to meet the needs of industrial development, it is crucial to develop electrocatalysts that can be prepared on a large scale, can work efficiently for a long time at high current densities, and can withstand industrial-related conditions such as pressure and temperature.

[0004] As an electrocatalyst, a catalyst must be a conductive material and also possess characteristics such as high efficiency, durability, and low cost. Transition metal phosphide-based catalysts have high conductivity, but currently, metal phosphides as electrocatalysts still suffer from insufficient exposure of active sites, limiting further improvements in hydrogen evolution performance during water electrolysis. CN115863064A discloses a molybdenum-doped nickel sulfide / nickel phosphide self-supporting heterojunction electrode and its preparation method. Mo-Ni3S2 is generated on an NF substrate through a two-stage hydrothermal method, followed by phosphating treatment to obtain a molybdenum-doped nickel sulfide / nickel phosphide self-supporting heterojunction (Mo-Ni3S2 / ... 12 The P5@NF electrode method uses a hydrothermal synthesis of the catalyst, which has a long synthesis cycle and cumbersome steps, making it unsuitable for large-scale and mass production. CN115537863A provides a method for preparing a three-dimensional ordered mesoporous nickel phosphide hydrogen evolution powder material. This method involves synthesizing a precursor powder through hydrothermal treatment and multiple solvent evaporation processes, followed by multiple calcinations to obtain the final product. This process is time-consuming and cumbersome. This nickel phosphide hydrogen evolution powder material exhibits performance at 100 mA / cm². -2 The overpotential at current density is around 340mV, indicating that the hydrogen evolution performance of the catalyst material needs to be improved.

[0005] Therefore, it is necessary to develop low-power, high-stability hydrogen evolution electrodes to reduce the cost of hydrogen production through water electrolysis and to achieve large-scale industrialization. Summary of the Invention

[0006] To address the above problems, this invention provides a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, its preparation method, and its application.

[0007] This invention proposes the following solution:

[0008] A lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode includes a foam metal substrate, a phosphide layer on the surface of the foam metal substrate, and a NiMoCuLa layer on the surface of the phosphide layer. The phosphide is obtained by phosphating the foam metal substrate, and the NiMoCuLa is a NiMo material co-doped with Cu and La.

[0009] Preferably, the foamed metal substrate is nickel foam, iron foam, or copper foam; the NiMoCuLa layer is obtained by electrodeposition.

[0010] As a general inventive concept, the present invention also provides a method for preparing a lanthanum copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, comprising:

[0011] (1) Provide a foamed metal as a substrate and phosphate it;

[0012] (2) Dissolve soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water and adjust the pH value to 7-10 to prepare an electroplating solution;

[0013] (3) Using the phosphated foam metal as the cathode and the graphite rod as the anode, electrodeposition is performed in the electroplating solution to form a Cu and La co-doped NiMo material coating on the phosphated foam metal, thus obtaining a lanthanum copper doped nickel molybdenum / nickel phosphide self-supporting electrode.

[0014] Preferably, in step (1), the phosphating treatment includes: placing the phosphorus source and the foam metal in a crucible, placing them upstream and downstream of the gas flow in the furnace body respectively, and calcining them in an inert gas or nitrogen atmosphere.

[0015] Optionally, the phosphorus source is sodium hypophosphite or red phosphorus;

[0016] Preferably, the calcination temperature is 250-400℃ and the calcination time is 10-60 min.

[0017] Preferably, in step (2), the molar ratio of soluble nickel salt to soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 3-7:0.14-3:0.01-0.09:0.01-0.1.

[0018] Optionally, the soluble lanthanum salt is at least one of lanthanum chloride, nitrate, and acetate.

[0019] The citrate is trisodium citrate;

[0020] The soluble nickel salt is at least one of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate;

[0021] The soluble molybdenum salt is at least one of ammonium molybdate, sodium molybdate, and potassium molybdate.

[0022] The soluble copper salt is at least one of copper sulfate, copper chloride, copper nitrate, and copper acetate.

[0023] Preferably, in step (2), the concentration of the soluble nickel salt in the electroplating solution is 0.21-0.42 mol / L; the concentration of the soluble molybdenum salt is 0.01-0.28 mol / L; the concentration of the soluble lanthanum salt is 0.0014-0.007 mol / L; the concentration of the soluble copper salt is 0.0014-0.0056 mol / L; and the concentration of citric acid or citrate is 0.25-0.45 mol / L.

[0024] Preferably, in step (2), saccharin and sodium sulfate are added when preparing the plating solution; the concentration of saccharin in the plating solution is 0.5-2.5 g / L; and the concentration of sodium sulfate is 10-40 g / L.

[0025] Preferably, in step (3), the electrodeposition temperature is 25-50°C; and the electrodeposition current density is 80-110 mA cm⁻¹. -2 The electrodeposition time is 10-60 min.

[0026] Preferably, in step (1), the foam metal is pretreated foam metal; the pretreatment includes: cutting the foam metal, then ultrasonically cleaning it sequentially with hydrochloric acid, anhydrous ethanol and deionized water, and then drying it.

[0027] As a general inventive concept, the present invention also provides an application of the aforementioned lanthanum copper-doped nickel molybdenum / nickel phosphide self-supporting electrode in water electrolysis.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention provides a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode. It uses a foamed metal substrate, on which a phosphating metal layer and a Cu / La co-doped NiMo layer are sequentially formed. The phosphating treatment alters the surface morphology and conductivity of the substrate material, increases the loading sites on the substrate surface, and consequently increases the active sites of the Cu / La co-doped NiMo material. This enhances the bonding strength between the nickel-molybdenum-lanthanum-copper and the substrate, promotes electron transfer, shortens the electron transport channel, and improves its electrocatalytic hydrogen evolution activity. Therefore, this electrode has advantages such as low hydrogen evolution overpotential, good conductivity, high electrochemical stability and catalytic activity, long service life, and low cost.

[0030] 2. This invention first treats the foamed metal using a phosphating process to modify its surface, increasing both the roughness and surface area of ​​the foamed metal substrate and improving its conductivity. The in-situ growth of phosphides on the foamed metal also ensures the mechanical stability of the substrate material. Then, a Cu-La co-doped NiMo layer is electrodeposited on the phosphated substrate surface. The newly added loading sites after phosphating provide more active sites for electrodeposition, and the electrodeposited Cu-La co-doped NiMo material exhibits excellent hydrogen evolution performance. Furthermore, the increased conductivity (increased electron transport rate) from phosphating effectively improves electrochemical performance (such as hydrogen evolution performance) in alkaline electrolytes, enhancing electrochemical stability and catalytic activity. The rough surface of the phosphated substrate also improves the bonding force between the electrodeposited layer and the phosphated substrate, further enhancing the material's mechanical stability. Therefore, the catalytic electrode catalyst prepared by this invention has a strong bond with the substrate, good catalytic activity and electrochemical stability, low hydrogen evolution overpotential, and long service life. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The images show SEM images of the materials after different treatments in Example 1, where (a) is the SEM image of the pretreated conductive substrate material; and (b) is the SEM image of the Ni obtained after phosphating. x SEM image of P / NF composite material; (c) shows NiMoLaCu@Ni obtained after electrodeposition. x SEM images of P / NF materials.

[0033] Figure 2The graph shows a comparison of the hydrogen evolution curves of the samples prepared in Example 1 and Comparative Examples 1 and 2, as well as the hydrogen evolution curves of nickel foam and platinum in 1 mol / L KOH solution.

[0034] Figure 3 The samples prepared for NF, as well as Comparative Example 1 and Example 1, were tested at 50 mA / cm. -2 Comparison of stability tests under current density. Detailed Implementation

[0035] This invention provides a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, comprising a foam metal substrate, a phosphide layer on the surface of the foam metal substrate, and a NiMoCuLa layer on the surface of the phosphide layer. The phosphide is obtained by phosphating the foam metal substrate, and the NiMoCuLa is a NiMo material co-doped with Cu and La.

[0036] In some preferred embodiments, the foamed metal substrate is foamed nickel, foamed iron, or foamed copper, more preferably foamed nickel. When the foamed metal substrate is foamed nickel, the phosphide is Ni. x P, where 2≤x≤3, and the value of x depends on the degree of phosphating; the NiMoCuLa layer is obtained by electrodeposition.

[0037] This invention employs phosphating and electrodeposition processes to prepare a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode. Phosphating the surface of a foamed metal yields a roughened phosphating metal material. Electrodeposition of nickel-molybdenum-lanthanum-copper material is then performed on this phosphating metal material substrate, resulting in a composite material with high conductivity, strong bonding, low hydrogen evolution potential, and good stability. For example, the composite material with nickel-molybdenum-lanthanum-copper loaded on nickel phosphide exhibits a conductivity of 100 mA × cm⁻¹. -2 The hydrogen evolution overpotential is as low as 78 mV at current density, and at 50 mA.cm -2 At current density, after 60 hours of hydrogen evolution testing, the overpotential decreased by only 35mV.

[0038] This invention specifically provides a method for preparing a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, comprising:

[0039] (1) Provide a foamed metal as a substrate and phosphate it;

[0040] (2) Dissolve soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water, and adjust the pH value to 7-10 to prepare the electroplating solution; if the pH value of the plating solution is too low, the concentration of free hydrogen ions in the solution will be too high, the hydrogen evolution reaction will be serious, and cracks and pits will easily appear in the coating, which will reduce the adhesion and performance of the coating. If the pH value is too high, during the electrodeposition process, H +The consumption of [agent] causes the pH value of the solution to rise, and nickel hydroxide precipitate appears near the cathode and is mixed in the coating, which increases the brittleness of the coating and affects the stability and composition of complex ions in the solution. Therefore, it is necessary to select an appropriate pH range to better improve the coating performance.

[0041] (3) Using the phosphated foam metal as the cathode and the graphite rod as the anode, electrodeposition is performed in the electroplating solution to form a Cu and La co-doped NiMo material coating on the phosphated foam metal, thereby obtaining a lanthanum copper doped nickel molybdenum / nickel phosphide self-supporting electrode.

[0042] In some preferred embodiments, step (1) of the phosphating treatment includes: placing the phosphorus source and foamed metal in a crucible, placing them upstream and downstream of the gas flow in the furnace body respectively, calcining them in an inert gas or nitrogen atmosphere, and finally cooling them to room temperature before removing the porcelain boat. In some preferred embodiments, 0.5-2g of sodium hypophosphite is weighed as the phosphorus source, and the weighed sodium hypophosphite is ground into powder in a mortar. The powder form can increase the surface area of ​​the sodium hypophosphite, making the phosphating more complete.

[0043] In some specific embodiments, the phosphorus source is sodium hypophosphite or red phosphorus.

[0044] In some preferred embodiments, the calcination temperature is 250-400℃, and the calcination time is 10-60 minutes. If the calcination temperature is too low, the sodium hypophosphite will not volatilize, making phosphating difficult; if the temperature is too high, the material will become brittle, compromising its mechanical stability.

[0045] In some preferred embodiments, in step (2), the molar ratio of soluble nickel salt to soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 3-7:0.14-3:0.01-0.09:0.01-0.1.

[0046] In some specific embodiments, the soluble lanthanum salt is at least one of lanthanum chloride, nitrate, and acetate;

[0047] The citrate is trisodium citrate;

[0048] The soluble nickel salt is at least one of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate;

[0049] The soluble molybdenum salt is at least one of ammonium molybdate, sodium molybdate, and potassium molybdate.

[0050] The soluble copper salt is at least one of copper sulfate, copper chloride, copper nitrate, and copper acetate.

[0051] In a preferred embodiment, in step (2), the concentration of the soluble nickel salt in the electroplating solution is 0.21-0.42 mol / L; the concentration of the soluble molybdenum salt is 0.01-0.28 mol / L; the concentration of the soluble lanthanum salt is 0.0014-0.007 mol / L; and the concentration of the soluble copper salt is 0.0014-0.0056 mol / L.

[0052] In some preferred embodiments, in step (2), the concentration of citric acid or citrate in the electroplating solution is 0.25-0.45 mol / L. With increasing citric acid content, more nickel-molybdenum metal ions are complexed with citrate, increasing cathode polarization. The electrodeposited coating becomes more uniform and fine, with a larger surface area and improved hydrogen evolution performance. However, when there is too much complexing agent, the stability of the complex formed by citrate and metal ions increases, making it more difficult for the coordinated metal ions to discharge, reducing cathode current efficiency, increasing the difficulty of metal deposition, and exacerbating hydrogen evolution. Excessive hydrogen evolution makes the coating loose and porous with poor adhesion, making it prone to detachment, thus reducing the hydrogen evolution catalytic activity of the coating.

[0053] In a preferred embodiment, in step (2), saccharin and sodium sulfate are added when preparing the plating solution; the concentration of saccharin in the plating solution is 0.5-2.5 g / L; the concentration of sodium sulfate is 10-40 g / L. The sulfur, nitrogen, and oxygen atoms in saccharin can provide lone pairs of electrons, generating a strong adsorption effect on the surface of nickel, inhibiting the growth of nickel grains. Simultaneously, saccharin increases the cathode deposition potential, reducing the deposition rate of nickel ions. Excessive saccharin reduces the cathode current efficiency, mainly because excessive nickel sulfide is generated in the plating layer. Nickel sulfide mixed in the plating layer reduces its brittleness and corrosion resistance. Appropriate amounts of sodium sulfate can increase the ionic conductivity in the plating solution, improve the dispersion ability of the plating solution, and reduce power consumption.

[0054] In a preferred embodiment, in step (3), the electrodeposition temperature is 25-50°C; the electrodeposition current density is 80-110 mA cm⁻¹. -2 The electrodeposition time is 10-60 minutes. In some specific embodiments, after electrodeposition, the sample is rinsed multiple times with deionized water and anhydrous ethanol, and then vacuum dried.

[0055] In some preferred embodiments, in step (1), the foam metal is a pretreated foam metal; the pretreatment includes: cutting the foam metal, then ultrasonically cleaning it sequentially with hydrochloric acid, anhydrous ethanol, and deionized water, and then drying it. For example, the conductive substrate foam can be ultrasonically treated in a 1-3M hydrochloric acid (HCl) solution for 10-20 minutes, then ultrasonically treated in anhydrous ethanol and deionized water sequentially for 5-15 minutes, and then dried in a vacuum drying oven for 12 hours. The purpose of the pretreatment is to remove oil and impurities from the NF surface. Simultaneously, the NF surface is rough due to acid corrosion, making it easier for materials to adhere during electrodeposition.

[0056] As a general inventive concept, the present invention also provides an application of the aforementioned lanthanum copper-doped nickel molybdenum / nickel phosphide self-supporting electrode in water electrolysis.

[0057] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0058] Example 1

[0059] This embodiment prepares a NiMoLaCu@Ni x P / NF composite materials, specifically prepared by the following methods:

[0060] (1) Pretreatment of conductive substrate material: Cut 2*2 cm pieces of nickel foam (NF), sonicate in 3M hydrochloric acid (HCl) solution for 15 min, sonicate in anhydrous ethanol and deionized water for 10 min respectively, and dry in a vacuum drying oven for 12 h. The morphology of the pretreated conductive substrate material is then examined, such as... Figure 1 As shown in (a).

[0061] (2) Phosphating: Weigh 1g of sodium hypophosphite as the phosphorus source and grind it into powder in a mortar. Place the powdered sodium hypophosphite and nickel foam separately into ceramic crucibles and place them upstream and downstream of the gas flow in a tube furnace (upstream and downstream are relative terms, i.e., the phosphorus source is upstream to ensure that the sodium hypophosphite decomposes at a certain temperature, and the decomposition products pass over the surface of the metal foam with the gas flow to ensure the phosphating reaction proceeds). In an argon atmosphere, raise the temperature to 300℃ at a heating rate of 5℃ / min, then calcine at 300℃ for 30min, and finally cool to room temperature. Remove the ceramic boat to obtain Ni. x P / NF composite material. A portion of the samples were taken for morphology analysis; SEM images are shown below. Figure 1 As shown in (b).

[0062] (3) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 0.3 mol of trisodium citrate (C6H5O7Na3), 0.0056 mol of hydrated lanthanum chloride (LaCl3×7H2O), and 0.0014 mol of pentahydrate copper sulfate (CuSO4×5H2O) were dissolved in 200 mL of deionized water. The trisodium citrate solution and ammonium molybdate tetrahydrate solution were added sequentially to the nickel sulfate hexahydrate solution, followed by 2 g of saccharin (C7H5NO3S) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O). The mixture was stirred thoroughly, and then lanthanum chloride heptahydrate (LaCl3×7H2O) and copper sulfate pentahydrate (CuSO4×5H2O) were added to the mixed solution. The mixed solution was transferred to a 1 L volumetric flask, and deionized water was added to bring the volume to a final volume. The pH of the mixed solution was adjusted to 9 with ammonia.

[0063] (4) Electrodeposition: The plating solution was placed in a water bath and maintained at 35°C. The phosphated NF substrate material was placed in the plating solution as the cathode, and a graphite rod was used as the anode. Electrodeposition was performed using a two-electrode system. The electrodeposition current density was 100 mA × cm⁻¹. -2 The deposition time was 30 min. After deposition, the material was rinsed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for 12 h to obtain NiMoLaCu (i.e., La and Cu co-doped NiMo material)@Ni. x P / NF materials, morphology analysis of samples, SEM images as follows. Figure 1 As shown in (c).

[0064] Example 2

[0065] The only difference between this embodiment and embodiment 1 is that the calcination temperature in step (2) is different. In this embodiment, the calcination temperature is 350°C.

[0066] Example 3

[0067] The only difference between this embodiment and embodiment 1 is that the calcination temperature in step (2) is different. In this embodiment, the calcination temperature is 400℃.

[0068] Example 4

[0069] The only difference between this embodiment and embodiment 1 is that the calcination time in step (2) is different. In this embodiment, the calcination time is 10 min.

[0070] Example 5

[0071] The only difference between this embodiment and embodiment 1 is that the calcination time in step (2) is different. In this embodiment, the calcination time is 50 min.

[0072] Comparative Example 1

[0073] This comparative example prepared a NiMoLaCu@NF material, which differed from Example 1 only in that the NF matrix was not phosphated. The specific method included:

[0074] (1) Pretreatment of conductive substrate material: cut 2*2 cm size nickel foam (NF), sonicate in 3M hydrochloric acid (HCl) solution for 15 min, sonicate in anhydrous ethanol and deionized water for 10 min in sequence, and dry in vacuum drying oven for 12 h.

[0075] (2) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 0.0056 mol of lanthanum chloride heptahydrate (LaCl3×7H2O) and 0.0014 mol of copper sulfate pentahydrate (CuSO4×5H2O) were dissolved in 200 mL of deionized water. The solutions of lanthanum chloride (LaCl3×7H2O) and lanthanum chloride (LaCl3×7H2O) were added sequentially to the nickel sulfate hexahydrate solution. The Cu / Mo molar ratio was 2%, and the La / Mo molar ratio was 8%. After thorough dissolution, the pH was adjusted to 9 with ammonia.

[0076] (3) Electrodeposition: The plating solution is placed in a water bath and maintained at 35°C. The substrate material is placed in the plating solution as the cathode, and a graphite rod is used as the anode. Electrodeposition is performed using a two-electrode system. The electrodeposition current density is 100 mA × cm⁻¹. -2 The deposition time was 30 min. After deposition, the sample was rinsed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for 12 h.

[0077] Comparative Example 2

[0078] This comparative example prepared a Ni x The P / NF material differs from Example 1 only in that NiMoLaCu was not deposited after phosphating the NF matrix. The specific method includes:

[0079] (1) Pretreatment of conductive substrate material: cut 2*2 cm size nickel foam (NF), sonicate in 3M hydrochloric acid (HCl) solution for 15 min, sonicate in anhydrous ethanol and deionized water for 10 min in sequence, and dry in vacuum drying oven for 12 h.

[0080] (2) Phosphating: Weigh 1g of sodium hypophosphite as the phosphorus source and grind it into powder in a mortar. Place the powdered sodium hypophosphite and nickel foam upstream and downstream of a ceramic crucible, respectively. In an argon atmosphere, raise the temperature to 300℃ at a heating rate of 5℃ / min, then calcine at 300℃ for 30min. Finally, cool to room temperature, remove the ceramic boat, and obtain Ni. x P / NF materials.

[0081] according to Figure 1 The SEM images show that (a) the NF surface is slightly corroded after pretreatment with hydrochloric acid solution, resulting in a slightly uneven surface; (b) the NF surface is covered with a Ni layer after phosphating. x P, increased surface roughness and larger specific surface area provide more loading sites for subsequent deposition of nickel-molybdenum-lanthanum-copper materials; (c) Figure shows uniformly grown nickel-molybdenum-lanthanum-copper particles, due to Ni x The rough surface of P leads to nickel-molybdenum-lanthanum-copper particles in Ni x The bonding on the P surface is stronger, and the specific surface area is larger, thus increasing the contact area.

[0082] The samples prepared in Example 1 and Comparative Examples 1 and 2, along with nickel foam and platinum, were used as working electrodes. Detection was performed in 1M KOH solution using a GAMRY electrochemical workstation. A three-electrode system was employed: a graphite rod as the counter electrode, an HgO electrode as the reference electrode, and a stainless steel electrode clamp as the working electrode. Hydrogen evolution performance was assessed using linear sweep voltammetry (LSV) at a current density of 100 mA × cm⁻¹. -2 The voltage value corresponding to the specified state. Generally, the lower the voltage value, the better the hydrogen evolution performance.

[0083] The resulting hydrogen evolution performance graph is shown below. Figure 2 As shown, from Figure 2 It can be seen that Ni is grown in situ on nickel foam. x P-materials do not significantly improve the hydrogen evolution performance of nickel foam; however, NiMoLaCu / NF materials obtained by depositing nickel-molybdenum-lanthanum-copper alloys on nickel foam exhibit excellent hydrogen evolution performance. NiMoLaCu@Ni is obtained by first phosphating the nickel foam and then depositing nickel-molybdenum-lanthanum-copper alloys. xThe hydrogen evolution performance of the P / NF composite material is further improved, reaching 100 mA×cm⁻¹. -2 The hydrogen evolution overpotential was as low as 78 mV at the current density. Based on the SEM image analysis, it is speculated that the reason for this phenomenon is that the surface roughness of NF increased after phosphating, resulting in a larger specific surface area. This increased the number of loading sites for nickel, molybdenum, lanthanum, and copper, thereby further improving the hydrogen evolution performance. In addition, the data in Table 1 show that the conductivity was improved after phosphating, which is another reason for the improved hydrogen evolution performance.

[0084] The results of the comparison with NF, the NiMoLaCu / NF obtained in Comparative Example 1, and the NiMoLaCu@Ni obtained in Example 1. x P / NF material at 50mA.cm -2 Stability tests were conducted at current density, and the results are as follows: Figure 3 As shown. From Figure 3 It can be seen that after 60 hours of testing, the performance of NF decreased by approximately 90mV (i.e., the overpotential increased by 90mV). The voltage-time curve of NiMoLaCu / NF showed large fluctuations, indicating poor material stability. Meanwhile, NiMoLaCu@Ni... x Compared to NF and NiMoLaCu / NF, P / NF materials exhibit better stability and a more stable curve. After 60 hours of testing, the overpotential increases by 35 mV.

[0085] Impedance tests were performed on NF, and the samples obtained from Comparative Example 2 and Examples 1-5, under open-circuit voltage. The results are shown in Table 1. The values ​​in Table 1 show that the Ni obtained from the phosphating treatment... x The impedance of P / NF materials decreases in Ni x A series of NiMoLaCu@Ni materials were obtained by electrodeposition of P / NF materials. x P / NF materials have lower impedance values ​​than NF materials, among which NiMoLaCu@Ni x The P / NF material (300℃ for 30 min) has the lowest impedance value and good electrical conductivity.

[0086] Table 1 Impedance values ​​for each material

[0087]

[0088] As can be seen from the above data, due to the preparation of NiMoLaCu@Ni x P / NF composite materials have advantages such as good conductivity, low overpotential, and good stability. Furthermore, nickel-molybdenum materials can be used as self-supporting materials with good mechanical properties and strong stability. Therefore, they can be directly used as hydrogen evolution electrodes for water electrolysis. Moreover, this material has the advantage of low cost when used as a hydrogen evolution electrode, making it suitable for large-scale industrial applications.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode, characterized in that, (1) Provide a foamed metal as a substrate and phosphate it; (2) Dissolve soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water and adjust the pH value to 7-10 to prepare an electroplating solution; (3) Using the phosphated foam metal as the cathode and the graphite rod as the anode, electrodeposition is performed in the electroplating solution to form a Cu and La co-doped NiMo material coating on the phosphated foam metal, thus obtaining a lanthanum copper doped nickel molybdenum / nickel phosphide self-supporting electrode. The supporting electrode includes a foam metal substrate, a phosphide layer on the surface of the foam metal substrate, and a NiMoCuLa layer on the surface of the phosphide layer. The phosphide is obtained by phosphating the foam metal substrate, and the NiMoCuLa is a NiMo material co-doped with Cu and La. In step (1), the phosphating treatment includes: placing the phosphorus source and foam metal in a crucible, placing them upstream and downstream of the gas flow in the furnace body respectively, and calcining them in an inert gas or nitrogen atmosphere; The phosphorus source is sodium hypophosphite or red phosphorus; the calcination temperature is 250-400℃; and the calcination time is 10-60 min.

2. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in claim 1, characterized in that, The foamed metal substrate is nickel foam, iron foam, or copper foam; the NiMoCuLa layer is obtained by electrodeposition.

3. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in claim 1, characterized in that, In step (2), the molar ratio of soluble nickel salt to soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 3-7:0.14-3:0.01-0.09:0.01-0.1; The soluble lanthanum salt is at least one of lanthanum chloride, nitrate, and acetate. The citrate is trisodium citrate; The soluble nickel salt is at least one of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate; The soluble molybdenum salt is at least one of ammonium molybdate, sodium molybdate, and potassium molybdate. The soluble copper salt is at least one of copper sulfate, copper chloride, copper nitrate, and copper acetate.

4. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in any one of claims 1 or 3, characterized in that, In step (2), the concentration of the soluble nickel salt in the electroplating solution is 0.21-0.42 mol / L; the concentration of the soluble molybdenum salt is 0.01-0.28 mol / L; the concentration of the soluble lanthanum salt is 0.0014-0.007 mol / L; the concentration of the soluble copper salt is 0.0014-0.0056 mol / L; and the concentration of citric acid or citrate is 0.25-0.45 mol / L.

5. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in claim 3, characterized in that, In step (2), saccharin and sodium sulfate were added when preparing the plating solution; the concentration of saccharin in the plating solution was 0.5-2.5 g / L; and the concentration of sodium sulfate was 10-40 g / L.

6. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in claim 3, characterized in that, In step (3), the electrodeposition temperature is 25-50℃; the electrodeposition current density is 80-110 mA cm⁻¹. -2 The electrodeposition time is 10-60 min.

7. The method for preparing the lanthanum-copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode as described in claim 3, characterized in that, In step (1), the foam metal is pretreated foam metal; the pretreatment includes: cutting the foam metal, then ultrasonically cleaning it in sequence with hydrochloric acid, anhydrous ethanol and deionized water, and then drying it.

8. The application of the copper-doped nickel-molybdenum / nickel phosphide self-supporting electrode prepared by any one of the preparation methods of claims 1-7 in water electrolysis.

Images