A self-supporting composite electrode of lamellar nickel selenide / vanadium selenide and a preparation method and application thereof

Abstract

The application discloses a lamellar nickel selenide / vanadium selenide self-supporting composite electrode of mallotus philippinensis and a preparation method and application thereof. In the preparation method, selenium powder is used as a selenium source, sodium dodecyl sulfate and polyvinylpyrrolidone are used as morphology control agents, a vanadium source and an alkali source are uniformly mixed, a nickel-vanadium-based hydroxide precursor is in-situ synthesized on a foam nickel by using a hydrothermal reaction method, selenium powder is added into the precursor, and an integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode is prepared by using a pyrolysis method. The application accelerates the redox process in the electrochemical reaction process, reduces the adsorption energy barrier of the reaction intermediate, and thus improves the catalytic performance of the material. On the other hand, the electron transfer in the electrocatalytic reaction process is improved, the catalytic activity is promoted, the strong interaction between the active material and the NF substrate can be effectively ensured, and the active material exhibits good mechanical stability and anti-deformation ability in the electrochemical application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalytic materials, and relates to a leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy, as a renewable energy source with wide sources, high efficiency, and clean and low carbon, is considered as an ideal choice to replace carbon-based fuels. Water electrolysis for hydrogen production technology stands out among many hydrogen production methods, because the electricity used can be supplied by renewable energy sources (such as solar energy, wind energy, tidal energy, etc.), the reaction raw material is abundant and easy to obtain, and the product is hydrogen and oxygen, which does not pollute the environment (Li, Z.; Sun, L.; Zhang, Y.; Han, Y.; Zhuang, W.; Tian, L.; Tan, W. Coupled and decoupled electrochemical water splitting for boosting hydrogen evolution: A review and perspective, Coordination Chemistry Reviews , 2024, 510: 215837.). Therefore, electrocatalytic water production of hydrogen is a promising method for sustainable production of green hydrogen. At present, noble metal Pt-based materials and Ru / Ir-based materials with high activity are the most widely used electrocatalytic materials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, but their high cost and scarcity of reserves seriously restrict their development and large-scale application. Therefore, it is crucial to develop low-cost, high-activity and high-stability large-current-density electrocatalysts.

[0003] In recent years, researchers have developed a series of non-noble metal-based catalysts, such as phosphides, sulfides, selenides, carbides and oxides, etc. Among them, transition metal selenides are considered as a potential bifunctional electrocatalytic material due to their rich reserves, metal-like properties and adjustable electronic structure (Fan, H.; Jiao, D.; Fan, J.; Wang, D.; Zaman, B.; Zhang, W.; Zhang, L.; Zheng, W.; Cui, X. Kinetically and thermodynamically expediting elementary steps via high-valence Cr-incorporated of nickel selenide for water electrolysis. Nano Research, 2024,17(3): 1199-1208. It is worth noting that nickel selenide exhibits unique physical and chemical properties in the field of photoelectrocatalysis, and has attracted widespread attention. However, the problems of less active site exposure and poor intrinsic activity of nickel selenide greatly limit the improvement of catalytic performance. In addition, the adsorption and desorption ability of hydrogen protons and oxygen-containing species in pure nickel selenide is insufficient, resulting in unsatisfactory activity (Zhai, L.; Lo, T.; Xu, Z.; Potter, J.; Mo, J.; Guo, X.; Tang, C.; Tsang, S.; Lau, S. In situ phase transformation on nickel-based selenides for enhanced hydrogen evolution reaction in alkaline medium, ACS Energy Letters , 2020, 5(8): 2483-2491. Therefore, the regulation of the surface and interface structure and the electronic structure of nickel selenide is an important strategy to improve the electrocatalytic performance. SUMMARY

[0004] The present application aims to provide a lamina tree-like nickel selenide / vanadium selenide self-supporting composite electrode and its preparation method and application. The generated Ni3Se2 / V5Se8 nanosheet presents a lamina tree-like structure and forms a porous array, improving the electrocatalytic activity of nickel selenide material and solving the problem of insufficient adsorption and desorption ability of hydrogen protons and oxygen-containing species in pure nickel selenide.

[0005] In order to achieve the above-mentioned purpose, the preparation method of the present application comprises the following steps:

[0006] S1, uniformly mix 6.17-17.21 mg of sodium dodecyl sulfate and 5.42-15.67 mg of polyvinylpyrrolidone, pour into 14-16 mL of ultrapure water, and stir uniformly to obtain solution A;

[0007] S2, uniformly mix 94.4-102.3 mg of vanadium source and 86-96 mg of alkali source, pour into 14-16 mL of ultrapure water, and stir uniformly to obtain solution B, and mix solution A and solution B thoroughly to obtain solution C;

[0008] S3, put the pretreated foam nickel into solution C, and react in a hydrothermal reaction kettle at 120-130℃ for 18-20h;

[0009] S4. After the hydrothermal reaction is complete, allow it to cool naturally to room temperature, remove the reacted nickel foam, wash and dry it to obtain the nickel vanadium-based hydroxide precursor.

[0010] S5. Place the precursor obtained in step S4 and 197~221.1 mg of selenium powder into a magnetic boat, place the magnetic boat in a tube furnace, evacuate the tube of the tube furnace, and heat to 430~470℃ at a rate of 5~10℃ / min for sintering reaction, and hold at the temperature for 1.8~2.2 h.

[0011] S6. After the heat treatment reaction is completed, a protective gas is introduced and the temperature is lowered to room temperature. The ceramic boat is then removed from the tube furnace, and the sample is taken out of the ceramic boat to obtain the integrated nickel selenide / vanadium selenide self-supporting composite electrode Ni3Se2 / V5Se8 / NF.

[0012] In step S1, magnetic stirring is used to stir the mixture evenly at 20~25℃.

[0013] In step S2, the vanadium source is one or more of vanadium chloride, sodium metavanadate, ammonium metavanadate, or vanadium acetylacetonate, and the alkali source is one or more of urea, sodium hydroxide, or potassium hydroxide. The stirring is done by magnetic stirring at 20-25°C until homogeneous.

[0014] In step S3, the pretreated nickel foam is ultrasonically cleaned in acetone solution for 12-17 minutes, then ultrasonically cleaned in 2-3 mol / L hydrochloric acid for 6-11 minutes, then rinsed alternately with anhydrous ethanol and ultrapure water 3-4 times, and finally vacuum dried at 20-30°C.

[0015] The hydrothermal reaction in step S3 is carried out in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 55-65%.

[0016] The washing process in step S4 involves alternating rinsing with ultrapure water and anhydrous ethanol 4-5 times; followed by drying at 65-75°C.

[0017] Step S5 involves evacuating the inside of the tubular furnace tube: first evacuate the tube, then fill it with a hydrogen-argon mixture, repeating this process three times to completely remove the air from the tube, and then evacuate the tube to create a vacuum environment.

[0018] The protective gas in step S6 is a hydrogen-argon mixture of 5% H2 and 95% Ar.

[0019] A nickel selenide / vanadium selenide self-supporting composite electrode with a leaf-like shape, prepared according to the above method.

[0020] The prepared nickel selenide / vanadium selenide self-supporting composite electrode with a leaf-like shape is applied in the electrocatalytic hydrogen evolution and oxygen evolution reactions under alkaline and neutral conditions.

[0021] Compared with the prior art, the specific beneficial effects of this invention are as follows:

[0022] 1) This invention employs a combined hydrothermal and pyrolysis method to prepare an integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode. First, a nickel-vanadium-based hydroxide precursor is synthesized in situ using a hydrothermal method. This method is simple to operate, has extremely low cost, easily controls particle size, exhibits good dispersibility, and produces high-purity products. The synthesized nickel-vanadium-based hydroxide precursor possesses unique layered structure, high specific surface area, and unique electronic structure. Subsequently, a pyrolysis method is used to achieve the transformation of the nickel-vanadium-based hydroxide into the Ni3Se2 / V5Se8 / NF phase. This method allows for control over the product's low particle size, high purity, and uniform morphology, making it suitable for large-scale production, reducing production costs, and improving production efficiency.

[0023] 2) The preparation method of the present invention uses two surfactants, sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP). The synergistic effect of SDS and PVP can not only prevent the nanoparticles from agglomerating to stabilize the reaction system, but also promote the full contact between the material and the electrolyte, expose more electrocatalytic active sites, thereby improving the apparent electrocatalytic activity of the material.

[0024] 3) In this invention, nickel foam (NF) not only provides a nickel source, but its three-dimensional porous structure also ensures that more active sites are exposed in the reaction medium, which is beneficial to increasing the effective loading of the catalyst and improving the diffusion rate of the reactants. At the same time, the integrated catalytic electrode synthesized in situ exhibits good mechanical stability and resistance to deformation in electrochemical applications. Furthermore, as a metal substrate, nickel foam has good conductivity, ensuring an efficient electron transport path, thereby improving the kinetics of the electrocatalyst in electrochemical reactions.

[0025] 4) This invention constructs a Ni3Se2 / V5Se8 heterostructure electrocatalyst on an NF substrate to enhance the electrocatalytic performance of the material. Specifically, the V element in vanadium selenide can regulate the electron density of the Ni sites in nickel selenide, modulating the adsorption and desorption capacity of these sites for hydrogen protons and oxygen-containing species. Simultaneously, it can improve the oxidation state of the Ni sites, accelerate the redox process in the electrochemical reaction, and reduce the adsorption energy barrier of reaction intermediates, thereby improving the intrinsic electrocatalytic activity of the material.

[0026] 5) When the material of this invention is used as an electrocatalyst, it exhibits excellent catalytic performance under both alkaline and neutral conditions. Under alkaline conditions, when the current density reaches 100 mA / cm², it achieves excellent catalytic performance. 2 The required HER and OER overpotentials are 168 mV and 280 mV, respectively. Under neutral conditions, when the current density reaches 100 mA / cm²,2 The required overpotentials for HER and OER are 252 mV and 390 mV, respectively, and the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode exhibits good high current density catalytic performance under both alkaline and neutral conditions.

[0027] In summary, the present invention features a simple preparation process, low production cost, short preparation cycle, easy process control, and easily adjustable composition and structure. The prepared composite material has a sheet-like array structure, exhibits a fast electron transfer rate, good catalytic activity, strong stability, and high hydrogen production efficiency. The nickel selenide / vanadium selenide (Ni3Se2 / V5Se8 / NF) self-supporting composite electrode prepared on a nickel foam substrate is applied in the field of electrocatalysis, demonstrating excellent high current density electrocatalytic HER and OER performance under both alkaline and neutral conditions. Attached Figure Description

[0028] Figure 1 This is the X-ray diffraction (XRD) pattern of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention.

[0029] Figure 2 This is a low-magnification scanning electron microscope (SEM) image of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention.

[0030] Figure 3 This is a high-magnification scanning electron microscope (SEM) image of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention.

[0031] Figure 4 This is a hydrogen production performance (HER) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under alkaline conditions, obtained by linear sweep voltammetry (LSV).

[0032] Figure 5 This is an oxygen production performance (OER) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under alkaline conditions, obtained by linear sweep voltammetry (LSV).

[0033] Figure 6 This is a hydrogen production performance (HER) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under neutral conditions, obtained by linear sweep voltammetry (LSV).

[0034] Figure 7 This is an oxygen production performance (OER) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under neutral conditions, obtained by linear sweep voltammetry (LSV). Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but this is not intended to limit the present invention.

[0036] Example 1:

[0037] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 12 min, then poured into prepared 2 mol / L hydrochloric acid and ultrasonically cleaned for 11 min, then rinsed 3 times alternately with anhydrous ethanol and ultrapure water, and finally vacuum dried at 24℃ for 12 h for later use.

[0038] 2) Mix 6.17 mg of sodium dodecyl sulfate and 5.42 mg of polyvinylpyrrolidone evenly, pour in 14 mL of ultrapure water, and stir magnetically at 20°C for 40 min until homogeneous to obtain solution A.

[0039] 3) Mix 94.4 mg of vanadium chloride and 86 mg of urea evenly, pour in 14 mL of ultrapure water, stir evenly to obtain solution B, and finally mix solution A with mixture B thoroughly and stir to obtain solution C; preferably, the stirring is done with magnetic stirring, and the stirring time is 40 min at 20℃.

[0040] 4) The pretreated nickel foam was placed in solution C and subjected to a hydrothermal reaction in a polytetrafluoroethylene (PTFE) hydrothermal reactor at a temperature of 120°C for 20 hours; solution C was reacted in the PTFE hydrothermal reactor with a filling ratio of 56%.

[0041] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves alternating rinsing with ultrapure water and anhydrous ethanol four times. The drying temperature is 65 °C and the time is 6 h.

[0042] 6) Place the precursor obtained in step 5) and 197 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with a hydrogen-argon mixed protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment again. Then carry out the sintering reaction in the tube furnace. Increase the temperature at a rate of 5 °C / min. The sintering reaction temperature is 430 °C and the holding time is 2.2 h.

[0043] 7) After the heat treatment reaction is completed, a hydrogen-argon mixed gas is introduced for protection. The mixing ratio is 5% H2 + 95% Ar. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0044] Figure 1 The X-ray diffraction (XRD) pattern of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention shows that there are three phases. The Ni peak (PDF#70-1849) originates from the nickel foam (NF) substrate, while the other two are the Ni3Se2 peak (PDF#19-0841) and V5Se8 peak (PDF#18-1455) grown on the NF substrate. This proves that the present invention has successfully prepared the Ni3Se2 / V5Se8 composite on the NF substrate.

[0045] Figure 2 This is a low-magnification scanning electron microscope (SEM) image of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of the present invention. It can be seen that the Ni3Se2 / V5Se8 nanosheets intersect and grow vertically on the NF substrate, forming a uniformly distributed nanosheet array morphology.

[0046] Figure 3 This is a high-magnification scanning electron microscope (SEM) image of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of the present invention. It can be seen that the Ni3Se2 / V5Se8 nanosheets exhibit a leaf-like structure of Koelreuteria paniculata and form a porous array.

[0047] Figure 4 This is a linear sweep voltammetry (LSV) curve (HER) of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under alkaline conditions. The Ni3Se2 / V5Se8 / NF electrode exhibits good electrocatalytic hydrogen production activity, with a current density reaching 100 mA / cm². 2 The required overpotentials are 168 mV.

[0048] Figure 5 This is a linear sweep voltammetry (LSV) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention, showing its oxygen evolution performance (OER) under alkaline conditions. The Ni3Se2 / V5Se8 / NF electrode exhibits good electrocatalytic oxygen evolution activity, with a current density reaching 100 mA / cm². 2 The required overpotentials are 280 mV.

[0049] Figure 6This is a linear sweep voltammetry (LSV) curve (HER) of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention under neutral conditions. The Ni3Se2 / V5Se8 / NF electrode exhibits good electrocatalytic hydrogen production activity, with a current density reaching 100 mA / cm². 2 The required overpotentials are 252 mV.

[0050] Figure 7 This is a linear sweep voltammetry (LSV) curve of the Ni3Se2 / V5Se8 / NF electrocatalytic electrode prepared in Example 1 of this invention, showing its oxygen evolution performance (OER) under neutral conditions. The Ni3Se2 / V5Se8 / NF electrode exhibits good electrocatalytic oxygen evolution activity, with a current density reaching 100 mA / cm². 2 The required overpotentials are 390 mV.

[0051] Example 2:

[0052] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 13 min, then poured into prepared 3 mol / L hydrochloric acid and ultrasonically cleaned for 8 min, then rinsed with anhydrous ethanol and ultrapure water alternately 4 times, and finally vacuum dried at 30℃ for 11 h for later use.

[0053] 2) Mix 8.5 mg of sodium dodecyl sulfate and 7.5 mg of polyvinylpyrrolidone evenly, pour in 14 mL of ultrapure water, and stir evenly to obtain solution A; preferably, the stirring is done with magnetic stirring at 21°C for 36 min.

[0054] 3) Mix 96 mg of ammonium metavanadate and 88 mg of urea evenly, pour in 14 mL of ultrapure water, and stir evenly to obtain solution B. Finally, mix solution A and B thoroughly and stir to obtain solution C; preferably, magnetic stirring is used, and the stirring time is 36 min at 21°C.

[0055] 4) The pretreated nickel foam is placed in solution C for a hydrothermal reaction at a temperature of 122°C for 19.6 h; preferably, solution C is reacted in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 56%.

[0056] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves alternating rinsing with ultrapure water and anhydrous ethanol four times. The drying temperature is 67℃ and the time is 5.8 h.

[0057] 6) Place the precursor obtained in step 5) and 202 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment. Then carry out the sintering reaction in the tube furnace. The temperature is increased at a rate of 6℃ / min. The sintering reaction temperature is 435℃ and the holding time is 2.1 h.

[0058] 7) After the heat treatment reaction is completed, a protective gas is introduced for protection. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The protective gas is a hydrogen-argon mixture with a mixing ratio of 5% H2 + 95% Ar. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0059] Example 3:

[0060] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 14 min, then poured into prepared 2 mol / L hydrochloric acid and ultrasonically cleaned for 10 min, then rinsed 3 times alternately with anhydrous ethanol and ultrapure water, and finally vacuum dried at 28℃ for 11 h for later use.

[0061] 2) Mix 10.5 mg of sodium dodecyl sulfate and 9.2 mg of polyvinylpyrrolidone evenly, pour in 15 mL of ultrapure water, and stir evenly to obtain solution A; preferably, the stirring is done with magnetic stirring at 22°C for 32 min.

[0062] 3) Mix 98 mg of sodium metavanadate and 90 mg of potassium hydroxide evenly, pour in 15 mL of ultrapure water, and stir evenly to obtain solution B. Finally, mix solution A and B thoroughly and stir to obtain solution C; preferably, magnetic stirring is used, and the stirring time is 32 min at 22℃.

[0063] 4) The pretreated nickel foam is placed in solution C for a hydrothermal reaction at a temperature of 125°C for 19.2 h; preferably, solution C is reacted in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 60%.

[0064] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves alternating rinsing with ultrapure water and anhydrous ethanol four times. The drying temperature is 70℃ and the time is 5.5 h.

[0065] 6) Place the precursor obtained in step 5) and 207 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment. Then carry out the sintering reaction in the tube furnace. The temperature is increased at a rate of 7℃ / min. The sintering reaction temperature is 440℃ and the holding time is 2.1 h.

[0066] 7) After the heat treatment reaction is completed, a protective gas is introduced for protection. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The protective gas is a hydrogen-argon mixture with a mixing ratio of 5% H2 + 95% Ar. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0067] Example 4:

[0068] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 15 min, then poured into prepared 3 mol / L hydrochloric acid and ultrasonically cleaned for 7 min, then rinsed alternately with anhydrous ethanol and ultrapure water 4 times, and finally vacuum dried at 26℃ for 12 h for later use.

[0069] 2) Mix 12.8 mg of sodium dodecyl sulfate and 11.5 mg of polyvinylpyrrolidone evenly, pour in 15 mL of ultrapure water, and stir evenly to obtain solution A; preferably, the stirring is done with magnetic stirring at 23°C for 30 min.

[0070] 3) Mix 100 mg of vanadium chloride and vanadium acetylacetonate in a 2:1 mass ratio with 92 mg of urea and potassium hydroxide in a 1:1 mass ratio until homogeneous. Pour in 15 mL of ultrapure water and stir until homogeneous to obtain solution B. Finally, mix solution A and B thoroughly and stir to obtain solution C. Preferably, magnetic stirring is used, and the stirring time is 30 min at 23°C.

[0071] 4) The pretreated nickel foam is placed in solution C for a hydrothermal reaction at a temperature of 126°C for 19 hours; preferably, solution C is reacted in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 60%.

[0072] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves rinsing with ultrapure water and anhydrous ethanol alternately 5 times. The drying temperature is 72℃ and the time is 5 hours.

[0073] 6) Place the precursor obtained in step 5) and 212 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment. Then carry out the sintering reaction in the tube furnace. Increase the temperature at a rate of 8℃ / min. The sintering reaction temperature is 450℃ and the holding time is 2 h.

[0074] 7) After the heat treatment reaction is completed, a protective gas is introduced for protection. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The protective gas is a hydrogen-argon mixture with a mixing ratio of 5% H2 + 95% Ar. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0075] Example 5:

[0076] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 16 min, then poured into prepared 2 mol / L hydrochloric acid and ultrasonically cleaned for 9 min, then rinsed 3 times alternately with anhydrous ethanol and ultrapure water, and finally vacuum dried at 22℃ for 13 h for later use.

[0077] 2) Mix 15 mg of sodium dodecyl sulfate and 13.5 mg of polyvinylpyrrolidone evenly, and pour in 16 mL of ultrapure water. Stir until homogeneous to obtain solution A. Preferably, magnetic stirring is used, and the stirring time is 25 min at 24 °C.

[0078] 3) Mix 101 mg of sodium metavanadate and ammonium metavanadate in a 1:1 mass ratio with 94 mg of sodium hydroxide and potassium hydroxide in a 1:1 mass ratio, pour the mixture into 16 mL of ultrapure water, and stir until homogeneous to obtain solution B. Finally, thoroughly mix solution A and B and stir to obtain solution C; preferably, magnetic stirring is used, and the stirring time is 25 min at 24°C.

[0079] 4) The pretreated nickel foam is placed in solution C for a hydrothermal reaction at a temperature of 128°C for 18.5 h; preferably, solution C is reacted in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 64%.

[0080] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves rinsing with ultrapure water and anhydrous ethanol alternately 5 times. The drying temperature is 73℃ and the time is 4.5 h.

[0081] 6) Place the precursor obtained in step 5) and 216 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment. Then carry out the sintering reaction in the tube furnace. The temperature is increased at a rate of 9℃ / min. The sintering reaction temperature is 460℃ and the holding time is 1.9 h.

[0082] 7) After the heat treatment reaction is completed, a protective gas is introduced for protection. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The protective gas is a hydrogen-argon mixture with a mixing ratio of 5% H2 + 95% Ar. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0083] Example 6:

[0084] 1) Pretreatment of nickel foam: First, cut nickel foam pieces of 5 cm × 1 cm × 0.15 cm in size were ultrasonically cleaned in acetone solution for 17 min, then poured into prepared 3 mol / L hydrochloric acid and ultrasonically cleaned for 6 min, then rinsed 4 times alternately with anhydrous ethanol and ultrapure water, and finally vacuum dried at 20℃ for 13 h for later use.

[0085] 2) Mix 17.2 mg of sodium dodecyl sulfate and 15.67 mg of polyvinylpyrrolidone evenly, pour in 16 mL of ultrapure water, and stir evenly to obtain solution A; preferably, the stirring is done with magnetic stirring at 25°C for 20 min.

[0086] 3) Mix 102.3 mg of vanadium acetylacetonate and 96 mg of sodium hydroxide evenly, pour in 16 mL of ultrapure water, stir evenly to obtain solution B, and finally mix solution A and B thoroughly and stir to obtain solution C; preferably, the stirring is done with magnetic stirring, and the stirring time is 20 min at 25℃.

[0087] 4) The pretreated nickel foam is placed in solution C for hydrothermal reaction at a temperature of 130°C for 18 hours; preferably, solution C is reacted in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 64%.

[0088] 5) After the hydrothermal reaction is completed, the product, nickel foam, is naturally cooled to room temperature. After washing and drying, the nickel-vanadium-based hydroxide precursor is obtained. The washing process involves rinsing with ultrapure water and anhydrous ethanol alternately 5 times. The drying temperature is 75℃ and the time is 4 hours.

[0089] 6) Place the precursor obtained in step 5) and 221.1 mg of selenium powder into a magnetic boat and place it in a tube furnace. Evacuate the tube furnace to create a vacuum environment. Place the magnetic boat in the tube furnace, first evacuate the vacuum, then fill it with protective gas. Repeat this process three times to remove all the air from the tube. Then evacuate the tube to create a vacuum environment. Then carry out the sintering reaction in the tube furnace. Increase the temperature at a rate of 10℃ / min. The sintering reaction temperature is 470℃ and the holding time is 1.8 h.

[0090] 7) After the heat treatment reaction is completed, a protective gas is introduced for protection. When the temperature drops to room temperature, the ceramic boat is taken out of the tube furnace. The protective gas is a hydrogen-argon mixture with a mixing ratio of 5% H2 + 95% Ar. The sample is taken out of the ceramic boat to obtain the integrated Ni3Se2 / V5Se8 / NF self-supporting composite electrode.

[0091] In this invention, the V element in vanadium selenide can regulate the electron density of the Ni sites in nickel selenide, thereby modulating the adsorption and desorption capacity of these sites for hydrogen protons and oxygen-containing species. Simultaneously, it can improve the oxidation state of the Ni sites, accelerate the redox process in the electrochemical reaction, and reduce the adsorption capacity of reaction intermediates, thus improving the catalytic performance of the material. Furthermore, the in-situ liquid-phase growth technique assisted by the structure regulator not only facilitates the full exposure of the electrochemically active sites of the catalytic material grown on its surface, improving electron transfer during the electrocatalytic reaction and promoting enhanced catalytic activity, but also effectively ensures a strong interaction between the active material and the NF substrate, resulting in good mechanical stability and resistance to deformation in electrochemical applications.

Claims

1. A method for preparing a leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode from Koelreuteria paniculata, characterized in that, Includes the following steps: S1. Mix 6.17–17.21 mg of sodium dodecyl sulfate and 5.42–15.67 mg of polyvinylpyrrolidone evenly, pour in 14–16 mL of ultrapure water, and stir evenly to obtain solution A; S2. Mix 94.4–102.3 mg of vanadium source and 86–96 mg of alkali source evenly, pour in 14–16 mL of ultrapure water, stir evenly to obtain solution B, mix solution A and solution B thoroughly, and stir to obtain solution C; S3. Place the pretreated nickel foam into solution C and react it in a hydrothermal reactor at 120-130°C for 18-20 hours. S4. After the hydrothermal reaction is complete, allow it to cool naturally to room temperature, remove the reacted nickel foam, wash and dry it to obtain the nickel vanadium-based hydroxide precursor. S5. Place the precursor obtained in step S4 and 197-221.1 mg of selenium powder into a magnetic boat, place the magnetic boat in a tube furnace, evacuate the tube of the tube furnace, and heat to 430-470°C at a rate of 5-10°C / min for sintering reaction, and hold at the temperature for 1.8-2.2 h. S6. After the heat treatment reaction is completed, a protective gas is introduced and the temperature is lowered to room temperature. The ceramic boat is then removed from the tube furnace, and the sample is taken out of the ceramic boat to obtain the integrated nickel selenide / vanadium selenide self-supporting composite electrode Ni3Se2 / V5Se8 / NF.

2. The method for preparing a leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode of *Koelreuteria paniculata* according to claim 1, characterized in that, In step S1, magnetic stirring is used to stir the mixture evenly at 20-25°C.

3. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, In step S2, the vanadium source is one or more of vanadium chloride, sodium metavanadate, ammonium metavanadate, or vanadium acetylacetonate, and the alkali source is one or more of urea, sodium hydroxide, or potassium hydroxide. The stirring is done by magnetic stirring at 20-25°C until homogeneous.

4. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, In step S3, the pretreated nickel foam is ultrasonically cleaned in acetone solution for 12-17 minutes, then ultrasonically cleaned in 2-3 mol / L hydrochloric acid for 6-11 minutes, then rinsed alternately with anhydrous ethanol and ultrapure water 3-4 times, and finally vacuum dried at 20-30°C.

5. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, The hydrothermal reaction in step S3 is carried out in a polytetrafluoroethylene hydrothermal reactor with a filling ratio of 55-65%.

6. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, The washing in step S4 involves alternating rinsing with ultrapure water and anhydrous ethanol 4 to 5 times; followed by drying at 65 to 75°C.

7. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, Step S5 involves evacuating the inside of the tubular furnace tube: first evacuate the tube, then fill it with a hydrogen-argon mixture, repeating this process three times to completely remove the air from the tube, and then evacuate the tube to create a vacuum environment.

8. The method for preparing a Koelreuteria paniculata leaf-shaped nickel selenide / vanadium selenide self-supporting composite electrode according to claim 1, characterized in that, The protective gas in step S6 is a hydrogen-argon mixture of 5% H2 and 95% Ar.

9. A nickel selenide / vanadium selenide self-supporting composite electrode with a leaf-like shape, prepared by the method according to any one of claims 1-8.

10. The application of the nickel selenide / vanadium selenide self-supporting composite electrode with a goldenrain tree leaf shape as described in claim 9 in the electrocatalytic hydrogen evolution and oxygen evolution reactions under alkaline and neutral conditions.

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