A lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, its preparation method and application

Abstract

This invention provides a method for preparing a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, comprising: dissolving soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water, and adjusting the pH value to 7-10 to prepare a plating solution; using a foamed metal as a substrate and a graphite rod as an anode, electrodeposition is performed in the plating solution to obtain the electrode. Introducing copper into the nickel-molybdenum substrate reduces the electrode resistance, alters the microstructure and surface morphology of the nickel-molybdenum coating, and increases the number of active material particles on the foamed metal surface, thereby improving the electrode's hydrogen evolution performance. Lanthanum doping allows the 4f electron orbitals of lanthanum to combine with the 3d electron orbitals of transition metals, and the combination of lanthanum with transition metals nickel and molybdenum effectively regulates the electronic and crystal structure of the material. Furthermore, the large radius of lanthanum allows it to fill defects in the nickel-molybdenum crystal, causing lattice expansion in the nickel-molybdenum alloy and resulting in charge imbalance, further improving the electrode's catalytic performance.

Description

Technical Field

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

[0002] Human society's demand for traditional energy sources is increasing daily, while energy consumption leads to air pollution and the greenhouse effect, driving us to optimize energy management. Electro-to-gas technology is considered an effective energy management strategy, converting excess electricity into hydrogen—a green energy source with high energy density—through water electrolysis. Electricity costs account for over 80% of the cost of hydrogen production via water electrolysis. Therefore, reducing electricity consumption is key to cost reduction, and electrode performance directly affects hydrogen production electricity consumption. Thus, there is an urgent need to develop low-power, long-life catalyst materials to meet the ever-growing demand for hydrogen. However, currently, the best-performing catalyst material for water electrolysis hydrogen production is mainly Pt, which is expensive and limits its use in large-scale applications. Therefore, developing catalysts to replace precious metal materials and reduce the cost of hydrogen production through water electrolysis is an emerging global research topic.

[0003] Developing high-performance and inexpensive non-precious metal electrode materials is a crucial issue that urgently needs to be addressed to advance the large-scale application of water electrolysis for hydrogen production. Among various electrocatalyst materials, nickel-molybdenum-based materials are considered one of the most promising alkaline hydrogen production catalysts due to their excellent hydrogen evolution activity.

[0004] China Huaneng Group Clean Energy Technology Research Institute Co., Ltd. has invented a method for the industrial preparation of nickel-molybdenum electrodes (CN 115110112 A). This method utilizes high-energy ball milling to alloy nickel-aluminum alloy powder with molybdenum powder, obtaining a powder catalyst. The process is carried out at 100 mA cm⁻¹. -2 The hydrogen evolution overpotential at the current density is close to 100 mV. The catalyst powder prepared by this method needs to be mixed with a binder and repeatedly brushed onto the electrode substrate, followed by calcination in a muffle furnace to obtain the electrode material. This method suffers from problems with the adhesion between the catalyst and the electrode, and the multiple brushing process is cumbersome. Yang Chao et al. from Shanghai University invented a method for preparing nickel-molybdenum-copper ternary metal phosphides (CN 113428847 A), using a hydrothermal method and phosphating treatment to obtain nickel-molybdenum-copper phosphides. The composite material exhibits a hydrogen evolution overpotential of approximately 100 mV at 100 mA cm⁻¹. -2At current density, the hydrogen evolution overpotential is close to 500 mV, which is too high and the performance cannot meet the requirements for industrial applications. Meanwhile, the hydrothermal synthesis method has a long cycle and low efficiency, making it difficult to apply to the production of large-area materials. Furthermore, the synthesis of phosphides generates environmentally pollutants. Wuhu Midea Kitchen & Bath Appliances Manufacturing Co., Ltd. has invented a method for preparing cobalt-nickel-molybdenum based composite materials and their application in home appliances (CN114921704A). This method forms a cobalt-nickel-molybdenum alloy catalytic coating on the surface of a copper substrate by electrodeposition at 100 mA cm⁻¹. -2 The hydrogen evolution overpotential at current density is close to 250 mV, and the substrate preparation process is complex. Currently, the hydrogen evolution catalytic performance of nickel-molybdenum electrocatalytic electrode materials needs further improvement, and their long-term application suffers from stability issues.

[0005] CN114959776A discloses a method for preparing a three-dimensional porous Ni-Mo-Cu catalyst for reducing bubble drag in seawater electrolysis for hydrogen production. However, the prepared Ni-Mo-Cu catalyst exhibits a high hydrogen evolution overpotential, reaching 100 mA cm⁻¹. -2 The hydrogen evolution overpotential at current density is close to 340 mV, and further heat treatment is needed to improve its corrosion resistance in seawater.

[0006] Therefore, there is a need to develop low-power, high-stability nickel-molybdenum-based hydrogen evolution electrodes to reduce the cost of hydrogen production through water electrolysis and to achieve large-scale industrialization. To address existing technological problems and further improve the hydrogen evolution performance and stability of nickel-molybdenum-based materials, this invention provides a method for preparing a nickel-molybdenum-lanthanum-copper quaternary metal material and its applications. The raw materials used are abundant, inexpensive, and environmentally friendly. Furthermore, the synthesis method used in this invention is simple to operate, avoids polluting phosphating processes, is easy to control, and can be industrialized. Summary of the Invention

[0007] To address the above problems, this invention provides a hydrogen evolution electrode made of nickel-molybdenum-lanthanum-copper quaternary metal composite material, its preparation method, and its application.

[0008] To address the aforementioned technical issues, the following solutions are proposed:

[0009] A method for preparing a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, comprising:

[0010] S1. 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 plating solution;

[0011] S2. Using foamed metal as the substrate and graphite rod as the anode, electrodeposition is performed in the electroplating solution to obtain the product.

[0012] Preferably, in step S1, the molar ratio of soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 3-7:0.14-3:0.01-0.09:0.01-0.1, more preferably 4-7:0.5-2:0.03-0.09:0.01-0.06, even more preferably 4-7:0.8-1.5:0.03-0.09:0.01-0.06, and most preferably 5-7:1-1.1:0.05-0.09:0.01-0.05.

[0013] Preferably, in step S1, 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.

[0014] Preferably, in step S1, 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.

[0015] Preferably, in step S1, the soluble lanthanum salt is at least one of lanthanum chloride, nitrate, and acetate.

[0016] The citrate is trisodium citrate;

[0017] The soluble nickel salt is at least one of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate;

[0018] The soluble molybdenum salt is at least one of ammonium molybdate, sodium molybdate, and potassium molybdate.

[0019] The soluble copper salt is at least one of copper sulfate, copper chloride, copper nitrate, and copper acetate;

[0020] The foam metal is foamed nickel, foamed copper, or foamed iron.

[0021] Preferably, in step S2, 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.

[0022] Preferably, before electrodeposition, the foam metal is further subjected to pretreatment; the pretreatment includes cutting the foam metal, then ultrasonically cleaning it sequentially with hydrochloric acid, anhydrous ethanol and deionized water, and then drying it.

[0023] Preferably, in step S2, after electrodeposition is completed, the conductive substrate is removed and cleaned and dried.

[0024] As a general inventive concept, the present invention also provides a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, which is prepared by the preparation method described above.

[0025] As a general inventive concept, the present invention also provides the aforementioned lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode for use in water electrolysis to produce hydrogen.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention introduces copper into nickel-molybdenum (NiMo), which not only improves conductivity and reduces electrode resistance, but also alters the microstructure and surface morphology of the NiMo coating. Furthermore, the introduction of copper increases the number of active material particles on the foamed metal surface, resulting in a multi-faceted improvement in the electrode's hydrogen evolution performance. Simultaneously, doping NiMo with lanthanum has several advantages. First, lanthanum's 4f electron orbitals can bind with the 3d electron orbitals of transition metals, effectively regulating the electronic and crystal structure of the material. Second, lanthanum's large radius allows it to fill defects in the NiMo crystal, causing lattice expansion and charge imbalance, thereby further enhancing the electrode's catalytic performance.

[0028] 2. This invention can significantly reduce the hydrogen evolution overpotential and improve the electrode catalytic performance by simultaneously adding appropriate amounts of saccharin and sodium sulfate to the plating solution for preparing the catalyst. Attached Figure Description

[0029] 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.

[0030] Figure 1 The hydrogen evolution performance of samples prepared from nickel foam, platinum sheet, Comparative Example 1, Conditional Experiment Series 1, Conditional Experiment Series 2, and Examples 1-4 in 1 mol / L KOH solution is shown in (a) as a comparison of the hydrogen evolution performance of samples from nickel foam, platinum sheet, Comparative Example 1, and Conditional Experiment Series 1; (b) as a comparison of the hydrogen evolution performance of samples from nickel foam, platinum sheet, Comparative Example 1, and Conditional Experiment Series 2; and (c) as a comparison of the hydrogen evolution performance of samples from nickel foam, platinum sheet, Comparative Example 1, and Examples 1-4.

[0031] Figure 2SEM image (a) and EDS image (b) of NiMoLa; SEM image (c) and EDS image (d) of NiMoLaCu.

[0032] Figure 3 Hydrogen evolution curves of the material samples prepared for platinum sheet, nickel foam, Comparative Example 1, NiMo2%Cu, NiMo8%La and Example 1 in 1 mol / L KOH solution.

[0033] Figure 4 The impedance values ​​of the material samples prepared for nickel foam, Comparative Example 1, NiMo2%Cu, NiMo8%La and Example 1 were measured under open-circuit voltage.

[0034] Figure 5 The image shows a TEM image of NiMoLaCu prepared in Example 1.

[0035] Figure 6 Comparison of hydrogen evolution curves in 1 mol / L KOH solution for samples prepared in Examples 1, 5-7, including platinum sheets, nickel foam, and samples prepared in Examples 1-7. Detailed Implementation

[0036] This invention employs a one-step electrodeposition method, adding small amounts of lanthanum and copper to a nickel-molybdenum plating bath to prepare a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode. Due to the co-doping effect between La and Cu, the La and Cu co-doped nickel-molybdenum composite material exhibits high performance at 100 mA × cm⁻¹. -2 The hydrogen evolution overpotential can be significantly reduced at higher current densities, and the doping of nickel-molybdenum materials with lanthanum and copper elements significantly improves their performance. The specific technical solution is as follows:

[0037] A method for preparing a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, comprising:

[0038] S1. Electroplating Solution Preparation: Dissolve soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water, and adjust the pH to 7-10 to prepare the plating solution. If the pH of the plating solution is too low, the concentration of free hydrogen ions in the solution will be too high, leading to severe hydrogen evolution reaction, which can easily cause cracks and pitting in the coating, reducing the adhesion and performance of the coating. If the pH is too high, during the electrodeposition process, H... + The consumption of [agent] causes the pH value of the solution to rise, and nickel hydroxide precipitates appear near the cathode and become trapped in the coating, increasing the brittleness of the coating and affecting 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.

[0039] S2. Electrodeposition: Electrodeposition is carried out in the electroplating solution using foamed metal as the substrate and graphite rod as the anode to obtain the product.

[0040] In some preferred embodiments, in step S1, the molar ratio of the soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 3-7:0.14-3:0.01-0.09:0.01-0.1, more preferably 4-7:0.5-2:0.03-0.09:0.01-0.06, even more preferably 4-7:0.8-1.5:0.03-0.09:0.01-0.06, and most preferably 5-7:1-1.1:0.05-0.09:0.01-0.05.

[0041] In a preferred embodiment, in step S1, 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.

[0042] In some preferred embodiments, in step S1, saccharin and sodium sulfate are added when preparing the plating solution.

[0043] In some preferred embodiments, in step S1, 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. This results in a more uniform and finer electrodeposited coating 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. This reduces cathode current efficiency, increases the difficulty of metal deposition, and exacerbates hydrogen evolution. Excessive hydrogen evolution makes the coating porous, with poor adhesion, and prone to detachment, thus reducing the hydrogen evolution catalytic activity of the coating.

[0044] In a preferred embodiment, in step S1, the concentration of saccharin in the electroplating solution is 0.5-2.5 g / L. The sulfur, nitrogen, and oxygen atoms in saccharin can provide lone pairs of electrons, which generate a strong adsorption effect on the surface of nickel, inhibiting the growth of nickel grains. At the same time, saccharin also increases the cathode deposition potential, which reduces the deposition rate of nickel ions. Excessive saccharin will reduce the cathode current efficiency, mainly because excessive nickel sulfide is generated in the coating. Nickel sulfide mixed in the coating reduces the brittleness and corrosion resistance of the coating.

[0045] In some preferred embodiments, in step S1, the concentration of sodium sulfate in the electroplating solution is 10-40 g / L; an appropriate amount of sodium sulfate can increase the ionic conductivity in the plating solution, improve the dispersion ability of the plating solution, and reduce power consumption.

[0046] In some preferred embodiments, in step S1, 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 nitrate, and nickel acetate;

[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] The foam metal is foamed nickel, foamed copper, or foamed iron.

[0052] Temperature can, to some extent, represent the ease with which molecules diffuse in a plating bath. Higher temperatures result in faster molecular diffusion, a larger diffusion coefficient, and increased ion mobility. On the other hand, the temperature of the plating bath significantly affects the solution's resistance, the current distribution within the plating tank, and the deposition overpotential of metal ions, while also influencing the activation energy of electrocrystallization. Temperature causes changes in the concentration of metal ions near the cathode, thus significantly impacting the composition of the deposited layer. In some preferred embodiments, in step S2, the electrodeposition temperature is 25-50°C, and the electrodeposition current density is 80-110 mA cm⁻¹. -2 At lower current densities, the reduction rate of the metal is slow, or even nonexistent, but the deposited material is often dense and fine. Excessive current density leads to an overly rapid electrode reaction, resulting in a rough, loose, or burnt coating. During nickel-molybdenum electrodeposition, current density affects the deposition overpotential of nickel-molybdenum ions and the current efficiency of the cathode, thus influencing the morphology and performance of the coating. Therefore, to improve cathode efficiency and obtain a high-performance coating, a suitable current density range needs to be selected for electrodeposition; the electrodeposition time is typically 10-60 minutes.

[0053] In some preferred embodiments, prior to electrodeposition, the foamed metal undergoes a pretreatment process. This pretreatment includes cutting the foamed metal, followed by sequential ultrasonic treatment with hydrochloric acid, anhydrous ethanol, and deionized water, and then drying. This pretreatment not only removes oil and impurities from the NF surface but also roughens the surface of the NF due to acid corrosion, facilitating material adhesion during electrodeposition. Preferably, 1-3 mol / L hydrochloric acid is used for ultrasonic treatment for 10-20 minutes; ultrasonic treatment in anhydrous ethanol and deionized water takes 5-15 minutes.

[0054] In some preferred embodiments, step S2, after electrodeposition, further includes removing the conductive substrate for cleaning and drying.

[0055] As a general inventive concept, the present invention also provides a lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode, which is prepared by the preparation method described above.

[0056] As a general inventive concept, the present invention also provides the aforementioned lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode for use in water electrolysis to produce hydrogen.

[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] Comparative Example 1

[0059] This comparative example prepared a NiMo material, and the specific method included:

[0060] (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.

[0061] (2) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 0.3 mol of trisodium citrate (C6H5O7Na3) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O) were dissolved in 200 mL of deionized water. The trisodium citrate solution and ammonium molybdate tetrahydrate solution were added sequentially to nickel sulfate hexahydrate solution, followed by 2 g of saccharin (C7H5NO3S) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O), and stirred until homogeneous. The mixture was transferred to a 1 L volumetric flask, diluted to volume with deionized water, and the pH was adjusted to 9 with ammonia.

[0062] (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 material was rinsed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for 12 h to obtain Ni4Mo material.

[0063] Conditional Experiment Series 1

[0064] This experimental series prepared a series of copper-doped NiMo materials using specific methods, including:

[0065] (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.

[0066] (2) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 24 0.3 mol of trisodium citrate (C6H5O7Na3) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O) were dissolved in 200 mL of deionized water. The trisodium citrate solution and ammonium molybdate tetrahydrate solution were added sequentially to nickel sulfate hexahydrate solution, followed by 2 g of saccharin (C7H5NO3S) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O), and stirred until homogeneous. The mixture was transferred to a 1 L volumetric flask, and deionized water was added to bring the volume to a final depth. Copper sulfate pentahydrate (CuSO4×5H2O) was added to the mixture, with a Cu / Mo molar ratio of y (2%, 4%, 6%, 8%), and the corresponding material was named NiMoyCu. After homogeneity, the pH was adjusted to 9 with ammonia.

[0067] (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 material was rinsed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for 12 h to obtain NiMoCu material.

[0068] Conditional Experiment Series 2:

[0069] This experimental series prepared a series of lanthanum-doped NiMo materials using specific methods, including:

[0070] (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.

[0071] (2) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 240.3 mol of trisodium citrate (C6H5O7Na3) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O) were dissolved in 200 mL of deionized water. The trisodium citrate solution and ammonium molybdate tetrahydrate solution were added sequentially to nickel sulfate hexahydrate solution, followed by 2 g of saccharin (C7H5NO3S) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O), and stirred until homogeneous. The mixture was transferred to a 1 L volumetric flask, and deionized water was added to bring the volume to a final depth. Lanthanum chloride heptahydrate (LaCl3×7H2O) was added to the mixture, with a La / Mo molar ratio of x (2%, 4%, 6%, 8%, 10%), and the corresponding material was named NiMoxLa. After homogeneity, the pH was adjusted to 9 with ammonia.

[0072] (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 material was rinsed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven for 12 h to obtain NiMoLa material.

[0073] Example 1

[0074] This embodiment prepares a lanthanum and copper co-doped NiMo material, the specific method of which includes:

[0075] (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.

[0076] (2) Preparation of electroplating solution: Weigh 0.42 mol nickel sulfate hexahydrate (NiSO4×6H2O) and 0.07 mol ammonium molybdate tetrahydrate ((NH4)6Mo7O) 240.3 mol of trisodium citrate (C6H5O7Na3) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O) were dissolved in 200 mL of deionized water. The trisodium citrate solution and ammonium molybdate tetrahydrate solution were added sequentially to nickel sulfate hexahydrate solution, followed by 2 g of saccharin (C7H5NO3S) and 40 g of sodium crystalline sulfate decahydrate (Na2SO4×10H2O), and stirred until homogeneous. The mixture was transferred to a 1 L volumetric flask, and deionized water was added to bring the volume to a final volume. Lanthanum chloride heptahydrate (LaCl3×7H2O) and copper sulfate pentahydrate (CuSO4×5H2O) were then added to the mixture, with a Cu / Mo molar ratio of 2% and a La / Mo molar ratio of 8%. The corresponding material was named NiMoxLayCu. After homogeneous dissolution, the pH was adjusted to 9 with ammonia. The optimal molar masses for adding lanthanum chloride heptahydrate (LaCl3×7H2O) and copper sulfate pentahydrate (CuSO4×5H2O) are 0.0056 mol and 0.0014 mol, respectively.

[0077] (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 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 material.

[0078] Example 2

[0079] The only difference from Example 1 is that the Cu / Mo molar ratio is 4% and the La / Mo molar ratio is 6%.

[0080] Example 3

[0081] The only difference from Example 1 is that the Cu / Mo molar ratio is 6% and the La / Mo molar ratio is 4%.

[0082] Example 4

[0083] The only difference from Example 1 is that the Cu / Mo molar ratio is 8% and the La / Mo molar ratio is 2%.

[0084] Example 5

[0085] The only difference from Example 1 is that the addition of sodium sulfate decahydrate crystals is omitted.

[0086] Example 6

[0087] The only difference from Example 1 is that the addition of saccharin is omitted.

[0088] Example 7

[0089] The only difference from Example 1 is that the addition of saccharin and sodium sulfate decahydrate is omitted.

[0090] Comparative Example 2

[0091] The only difference from Example 1 is that ytterbium chloride hexahydrate is used instead of lanthanum chloride as a raw material to achieve Yb doping instead of La.

[0092] The samples prepared in the above examples and comparative examples were tested using a GAMRY electrochemical workstation in 1M KOH solution. A three-electrode system was used: a graphite rod as the counter electrode, an HgO electrode as the reference electrode, and the sample as the working electrode, which was held in stainless steel electrode clamps. Hydrogen evolution performance was tested using linear sweep voltammetry (LSV), observed 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.

[0093] The hydrogen evolution performance of samples prepared under alkaline conditions, including nickel foam, platinum sheets, Comparative Example 1, Conditional Experiment Series 1, Conditional Experiment Series 2, and Examples 1-4, was tested. The results are as follows: Figure 1 As shown in (a), 1(b) and 1(c), from Figure 1 (a) It can be seen that the addition of a small amount of Cu and a small amount of La to NiMo material can effectively reduce the hydrogen evolution overpotential of NiMo material, and the modification effect is the best when the Cu doping amount is 2% and the La doping amount is 8%. Figure 1 As can be seen from (a) and (b), doping with La and Cu respectively in NiMo improves the material performance. Doping with no La or too much La and Cu will affect the material performance. As can also be seen from 1(c), doping with appropriate amounts of Cu and La in NiMo at the same time has a significant effect on improving the performance of NiMo material.

[0094] Figure 2 Images (a) and (c) show the morphology of NiMo8%La and NiMo8%La2%Cu. The images reveal that NiMoLaCu particles are more uniform and regular. The corresponding EDS images show that the contents of Cu and La are trace compared to nickel and molybdenum, and that Cu and La are incorporated into the NiMo material. Comparing images (b) and (d), it is found that the addition of Cu increases the Mo content in the catalyst, and this increased Mo content is beneficial for performance improvement.

[0095] The hydrogen evolution curves of platinum sheet, nickel foam, Comparative Example 1, NiMo2%Cu, NiMo8%La and the material samples prepared in Example 1 in 1 mol / L KOH solution are shown in the figure. Figure 3 As shown, from Figure 3It can be seen that the NiMo material in Comparative Example 1 at 100 mA cm⁻¹ -2 The hydrogen evolution overpotential at the current density is 160 mV, and the NiMoLaCu composite material in Example 1 has a hydrogen evolution overpotential of 160 mV at 100 mA cm⁻¹. -2 The hydrogen evolution overpotential at the current density is 92 mV.

[0096] Table 1. Hydrogen evolution overpotential of the samples from Example 1 and Comparative Example 2 at different current densities in 1 mol / L KOH solution.

[0097]

[0098] Figure 4 The impedance values ​​of the material samples prepared for nickel foam, Comparative Example 1, NiMo2%Cu, NiMo8%La, and Example 1 were measured under open-circuit voltage. The diameter of the semicircular curve in the figure represents the charge transfer resistance value of the hydrogen evolution reaction. It can be seen that the impedance value of nickel foam is the highest, and the impedance value of NiMoLaCu is the lowest. The intersection of the curve with the x-axis represents the solution diffusion resistance. NiMoLaCu has the lowest solution diffusion resistance, indicating that the catalyst material is more easily contacted with the solution.

[0099] The NiMoLaCu material prepared in Example 1 was characterized by TEM, such as... Figure 5 As shown in the figure, the 0.18 nm and 0.201 nm lattice planes correspond to the (310) and (121) crystal planes of Ni4Mo. Due to the large radius of La, when doped into defects in NiMo material, NiMo undergoes lattice expansion, increasing its lattice spacing to 0.356 nm. Analysis shows that this change in lattice spacing causes charge imbalance, which can effectively improve the catalytic performance of the electrode.

[0100] The hydrogen evolution curves of platinum sheet, nickel foam, and samples prepared in Examples 1 and 5-7 in 1 mol / L KOH solution are compared as follows. Figure 6 As shown, from Figure 6 It can be seen that, compared with the sample without additives, the hydrogen evolution overpotential of the sample with saccharin alone is increased. Adding sodium sulfate decahydrate alone or adding both additives at the same time can effectively improve the hydrogen evolution overpotential of the sample, with the improvement effect of adding both additives at the same time being the best.

[0101] The overpotentials of the copper and lanthanum co-doped sample of Example 1 and the copper and ytterbium co-doped sample of Comparative Example 2 at different current densities are shown in Table 1 below. As can be seen from the table, the overpotential of the copper and lanthanum co-doped sample is significantly lower than that of the copper and ytterbium co-doped sample.

[0102] As can be seen from the above data, the prepared lanthanum and copper co-doped nickel-molybdenum material has good conductivity, low overpotential, and can be used as a self-supporting material with good mechanical properties and strong stability. Therefore, it can be directly used as a hydrogen evolution electrode for water electrolysis.

[0103] 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 and copper co-doped nickel-molybdenum hydrogen evolution electrode, characterized in that, include: S1. Dissolve soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, soluble copper salt, citric acid or citrate in water, and adjust the pH to 7-10 to prepare an electroplating solution; in step S1, the molar ratio of soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 4~7:1~1.1:0.05~0.09:0.01~0.05; in step S1, saccharin and sodium sulfate are also added when preparing the electroplating solution; in the electroplating solution, the concentration of saccharin is 0.5-2.5 g / L; the concentration of sodium sulfate is 10-40 g / L. S2. Using foamed metal as the substrate and a graphite rod as the anode, electrodeposition is performed in the electroplating solution to obtain a nickel-molybdenum hydrogen evolution electrode co-doped with lanthanum and copper.

2. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 1, characterized in that, In step S1, the molar ratio of soluble nickel salt, soluble molybdenum salt, soluble lanthanum salt, and soluble copper salt is 5~7:1~1.1:0.05~0.09:0.01~0.

05.

3. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 1, characterized in that, In step S1, 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.

4. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode according to any one of claims 1 to 3, characterized in that, In step S1, 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; The foam metal is foamed nickel, foamed copper, or foamed iron.

5. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 1, characterized in that, In step S2, the electrodeposition temperature is 25-50°C; the electrodeposition current density is 80-110 mA cm⁻¹. -2 The electrodeposition time is 10-60 min.

6. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 1, characterized in that, Prior to electrodeposition, the foam metal is pretreated; the pretreatment includes cutting the foam metal, then ultrasonically cleaning it sequentially with hydrochloric acid, anhydrous ethanol and deionized water, and then drying it.

7. The method for preparing the lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 1, characterized in that, In step S2, after electrodeposition is completed, the conductive substrate is removed and cleaned and dried.

8. A nickel-molybdenum hydrogen evolution electrode co-doped with lanthanum and copper, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 7.

9. The lanthanum and copper co-doped nickel-molybdenum hydrogen evolution electrode as described in claim 8 is applied to water electrolysis for hydrogen production.

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