A molybdenum-doped nickel phosphide electrode and its preparation method and application

Abstract

The present invention belongs to the field of electrochemical technology, and in particular to a molybdenum-doped nickel phosphide electrode and its preparation method and application. The preparation method includes: dissolving a soluble nickel salt, ammonium fluoride and urea in water to obtain a mixed solution; immersing nickel foam in the mixed solution for hydrothermal reaction to obtain a precursor Ni(CO3)OH / NF; immersing the precursor Ni(CO3)OH / NF in a molybdenum salt solution for solvent thermal reaction to obtain Mo‑Ni(OH)2 / NF; Mo‑Ni(OH)2 / NF and a phosphorus source are subjected to a high-temperature phosphating reaction in an inert atmosphere to obtain a molybdenum-doped nickel phosphide electrode. The present invention adopts a step-by-step doping method to not only overcome the problem that the prior art adds a nickel source and a molybdenum source at the same time, resulting in overlapping catalytic active sites and low catalytic efficiency, but also significantly increases the specific surface area of ​​the molybdenum-doped nickel phosphide electrode, so that the catalytic sites are more evenly distributed on its surface, thereby greatly improving the catalytic efficiency.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a molybdenum-doped nickel phosphide electrode and a preparation method and application thereof. Background Art

[0002] As a clean and sustainable method for producing hydrogen, water electrolysis technology holds immense importance in the context of global energy transition and climate change response. Hydrogen, with its high energy density, zero emissions, and ease of storage, is widely recognized as an ideal alternative energy source.

[0003] In the search for efficient methods to obtain hydrogen energy, electrolysis has emerged as a promising technology, and improving catalytic efficiency is highly dependent on the appropriate choice of catalyst. However, the development of water electrolysis hydrogen production technology still faces many challenges, including low hydrogen production efficiency, high overpotential required for the reaction, and high overall equipment costs. In particular, precious metal catalysts such as platinum, rhodium, and palladium, despite their excellent performance, are difficult to widely use due to their high price, which undoubtedly limits the commercialization of water electrolysis hydrogen production technology.

[0004] In the field of hydrogen energy research, molybdenum-doped nickel phosphide catalysts have broad application prospects, especially in the fields of hydrogen storage and hydrogen fuel cells. The main advantage of molybdenum-doped nickel phosphide catalysts lies in the regulatory effect of molybdenum atoms on the electronic properties of the catalyst surface. Molybdenum doping can introduce new electronic states, thereby changing the electron density and orbital distribution on the catalyst surface. This change helps to improve the adsorption capacity of molybdenum-doped nickel phosphide catalysts for hydrogen, thereby improving catalytic activity. In addition, molybdenum doping can also improve the stability of nickel phosphide catalysts. However, in the molybdenum-doped nickel phosphide electrodes currently prepared by simultaneously adding nickel and molybdenum sources, nickel and molybdenum form nickel clusters and molybdenum clusters, respectively, resulting in the overlap and stacking of molybdenum metal catalytic sites and nickel metal catalytic sites, which in turn makes the catalytic efficiency low, limiting its large-scale application in water electrolysis hydrogen production technology. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a molybdenum-doped nickel phosphide electrode and its preparation method and application. The present invention prepares a precursor Ni(OH)2 / NF by a hydrothermal method, then dopes the precursor Ni(OH)2 / NF with molybdenum to obtain Mo-Ni(OH)2 / NF; finally, mixes the Mo-Ni(OH)2 / NF with a phosphorus source and performs a high-temperature phosphating reaction to obtain a molybdenum-doped nickel phosphide electrode. The present invention adopts a step-by-step doping method to make the precursor Ni(CO3)OH / NF have a larger specific surface area, and then dopes molybdenum atoms into the lattice of nickel atoms, so that the catalytic sites of the molybdenum-doped nickel phosphide electrode obtained by the present invention are evenly distributed, thereby improving the catalytic efficiency of the molybdenum-doped nickel phosphide electrode, overcoming the problem of the molybdenum catalytic sites and nickel catalytic sites overlapping and stacking and low catalytic efficiency in the molybdenum-doped nickel phosphide electrode prepared by adding nickel source and molybdenum source at the same time in the prior art.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first object of the present invention is to provide a method for preparing a molybdenum-doped nickel phosphide electrode, comprising the following steps:

[0008] Dissolve soluble nickel salt, ammonium fluoride and urea in water to obtain a mixed solution; wherein the molar ratio of the soluble nickel salt, ammonium fluoride and urea is 0.5-1.5:4:5.

[0009] The metal foam is immersed in the mixed solution and subjected to a hydrothermal reaction to obtain the precursor Ni(CO3)OH / NF. In the hydrothermal reaction, urea and water are thermally decomposed to generate ammonia water, making the mixed solution weakly alkaline. At the same time, urea is thermally decomposed to generate carbonate ions. Under weak alkaline conditions, ammonium fluoride is used as a directing agent. Under the guiding effect of ammonium fluoride, nickel ions react with carbonate ions and hydroxide ions in the mixed solution to generate basic nickel carbonate, which is attached to the metal foam. - It is embedded into the layered structure of basic nickel carbonate to obtain Ni(CO3)OH / NF.

[0010] The precursor Ni(CO3)OH / NF is immersed in a molybdenum salt solution and subjected to a solvothermal reaction. During the solvothermal reaction, molybdenum ions diffuse into Ni(CO3)OH / NF and replace some nickel atoms to obtain Mo-Ni(OH)2 / NF.

[0011] The Mo-Ni(OH)2 / NF and the phosphorus source are placed at the upper and lower ends of a muffle furnace, respectively, and a high-temperature phosphating reaction is carried out in an inert atmosphere. During the high-temperature phosphating reaction, the PH3 gas generated by the decomposition of the phosphorus source at the upper end undergoes an oxidation-reduction reaction with the Ni(OH)2 in the Mo-Ni(OH)2 / NF at the lower end to obtain a molybdenum-doped nickel phosphide electrode.

[0012] Preferably, the concentration of molybdenum ions in the molybdenum salt solution is 0.2 mmol / L to 0.8 mmol / L; if the concentration of molybdenum ions is too low, the doping effect is poor, and if the concentration is too high, alloy formation occurs.

[0013] Preferably, the hydrothermal reaction conditions are: hydrothermal reaction at 90° C. to 150° C. for 5 h to 8 h.

[0014] Preferably, the conditions for the high-temperature phosphating reaction are: heating at 2°C / min to 250°C to 350°C for 1 hour to 3 hours.

[0015] Preferably, the soluble nickel salt is selected from nickel nitrate, nickel chloride or nickel sulfate; among them, compared with nickel chloride and nickel sulfate, nitrate is more stable in the chemical reaction of multiple metal ions and will not easily combine with other metal ions to form precipitates like chloride or sulfate ions.

[0016] Preferably, the molybdenum salt in the molybdenum salt solution is selected from Na2MoO4·2H2O or potassium molybdate.

[0017] Preferably, the metal foam is selected from nickel foam, titanium foam or copper foam.

[0018] Preferably, the phosphorus source is selected from sodium hypophosphite or red phosphorus.

[0019] Preferably, the Mo-Ni(OH)2 / NF is dried before the high temperature phosphating reaction. The drying conditions are: drying at 120°C to 150°C for 6h to 12h. 。

[0020] Preferably, the mass ratio of Mo-Ni(OH)2 / NF to the phosphorus source is 1:3 to 10; if the amount of the phosphorus source is too low, the molybdenum-doped nickel phosphide electrode will exhibit metallization characteristics, making the structure of the molybdenum-doped nickel phosphide electrode prone to change during the catalytic reaction, thereby reducing its stability; if the amount of the phosphorus source is too much, the molybdenum-doped nickel phosphide electrode will become phosphorus-rich, and the presence of a large number of PP bonds will weaken the conductivity of the molybdenum-doped nickel phosphide electrode, thereby reducing its catalytic efficiency.

[0021] The second object of the present invention is to provide a molybdenum-doped nickel phosphide electrode prepared by the above preparation method.

[0022] Preferably, in the molybdenum-doped nickel phosphide electrode, molybdenum atoms are doped into the lattice of nickel atoms.

[0023] Preferably, a molybdenum-doped nickel phosphide electrode is provided, wherein molybdenum-doped nickel phosphide is attached to the foam metal, the molybdenum-doped nickel phosphide is a nanosheet array, the nanosheets form a burr-like three-dimensional structure, and there are protruding molybdenum-doped nickel phosphide nanoparticles on the surface of the nanosheets, and uniform cavities are distributed on the surface of the three-dimensional structure.

[0024] The third object of the present invention is to provide the use of the above-mentioned molybdenum-doped nickel phosphide electrode in preparing a negative electrode for catalytic hydrogen evolution reaction.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention provides a method for preparing a molybdenum-doped nickel phosphide electrode, comprising dissolving a soluble nickel salt, ammonium fluoride, and urea in water to obtain a mixed solution; wherein the molar ratio of the soluble nickel salt, ammonium fluoride, and urea is 0.5-1.5:4:5; immersing a foamed metal in the mixed solution for a hydrothermal reaction to obtain a precursor Ni(CO3)OH / NF; during the hydrothermal reaction, urea and water are thermally decomposed to generate ammonia water, making the mixed solution weakly alkaline; and simultaneously, urea is thermally decomposed to obtain carbonate ions. Under weakly alkaline conditions, ammonium fluoride is used as a directing agent, and the F of ammonium fluoride is converted into carbonic acid. - with Ni 2+ The formation of complexes changes the Ni 2+ Under the guidance of ammonium fluoride, nickel ions react with carbonate ions and hydroxide ions in the mixed solution to form basic nickel carbonate, which is attached to the foam metal. - Embedded into the layered structure of basic nickel carbonate and maintaining the stability of the layered structure to obtain Ni(CO3)OH / NF; the precursor Ni(CO3)OH / NF is immersed in a molybdenum salt solution and subjected to a solvothermal reaction. During the solvothermal reaction, molybdenum ions diffuse into the Ni(CO3)OH / NF and replace some nickel atoms to obtain Mo-Ni(OH)2 / NF; the Mo-Ni(OH)2 / NF and a phosphorus source are placed at the upper and lower ends of a muffle furnace respectively, and a high-temperature phosphating reaction is carried out in an inert atmosphere. During the high-temperature phosphating reaction, PH3 gas generated by the decomposition of the phosphorus source at the upper end undergoes an oxidation-reduction reaction with the Mo-Ni(OH)2 / NF at the lower end to obtain a molybdenum-doped nickel phosphide electrode.

[0027] 2. The precursor Ni(CO3)OH / NF of the present invention has a large specific surface area and a regular layered structure, which is conducive to the uniform doping of molybdenum atoms and the uniform distribution of catalytic sites; the molybdenum atoms are uniformly doped into the lattice of nickel atoms, avoiding the phenomenon of nickel and molybdenum atoms agglomerating to form nickel clusters and molybdenum clusters respectively, so that the molybdenum catalytic sites and nickel catalytic sites are completely exposed, thereby effectively overcoming the problem of the existing technology of overlapping and stacking catalytic sites of molybdenum-doped nickel phosphide electrodes prepared by simultaneously adding nickel and molybdenum sources, which leads to low catalytic efficiency.

[0028] In addition, the high-temperature phosphating reaction of Mo-Ni(OH)2 / NF with phosphorus source does not change the overall structure of the precursor Ni(CO3)OH / NF and the doping state of molybdenum atoms. Therefore, the molybdenum-doped nickel phosphide electrode can maintain the uniformity of catalytic sites and high catalytic efficiency.

[0029] 3. The molybdenum-doped nickel phosphide electrode provided by the present invention exhibits higher activity and stability in the catalytic hydrogen evolution reaction. When the phosphide concentration is 0.8 mmol / L, the molybdenum-doped nickel phosphide electrode exhibits better catalytic hydrogen evolution performance, and the current density is 100 mA / cm 2 When , the overpotential is 278mV. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 These are morphology characterization images of the 0.8Mo-NiP / NF electrode of Example 4 of the present invention at different magnifications, where (a) is a lower magnification image and (b) is a higher magnification image.

[0031] Figure 2 This is the XRD spectrum of Ni(CO3)OH / NF of Example 2 of the present invention.

[0032] Figure 3 This is the XRD spectrum of Mo-Ni(OH)2 / NF of Example 3 of the present invention.

[0033] Figure 4 This is the XRD spectrum of the Mo-NiP / NF electrode of Example 4 of the present invention.

[0034] Figure 5 Ni(CO3)OH / NF, Mo-Ni(OH) 2 / LSV and EIS test diagrams of NF and Mo-NiP / NF electrodes, where (a) is the Ni(CO3)OH / NF, Mo-Ni(OH) 2 / LSV test diagram of NF and Mo-NiP / NF electrodes, (b) is Ni(CO3)OH / NF, Mo-Ni(OH) 2 / EIS test graphs of NF and Mo-NiP / NF electrodes.

[0035] Figure 6 These are the LSV and EIS test graphs of Ni(CO3)OH / NF and Mo-Ni(OH)2 / NF of Examples 1 to 4 of the present invention, wherein (a) is the LSV test graph of Ni(CO3)OH / NF and Mo-Ni(OH)2 / NF of Examples 1 to 4, and (b) is the EIS test graph of Ni(CO3)OH / NF and Mo-Ni(OH)2 / NF of Examples 1 to 4.

[0036] Figure 7These are the LSV and EIS test graphs of the Ni(CO3)OH / NF and Mo-NiP / NF electrodes of Examples 1 to 4 of the present invention, wherein (a) is the LSV test graph of the Ni(CO3)OH / NF and Mo-NiP / NF electrodes of Examples 1 to 4, and (b) is the EIS test graph of the Ni(CO3)OH / NF and Mo-NiP / NF electrodes of Examples 1 to 4. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solution of the present invention in conjunction with the data in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] It should be noted that the professional terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, the various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods. Among them, nickel nitrate hexahydrate, ammonium fluoride, and sodium molybdate dihydrate were all analytically pure and purchased from Shanghai Hushi; urea and sodium hypophosphite were both analytically pure, and potassium hydroxide was 91% pure and purchased from Aladdin.

[0039] Currently, molybdenum-doped nickel phosphide catalysts have shown great potential for application in hydrogen storage and hydrogen fuel cells. However, existing techniques for preparing molybdenum-doped nickel phosphide electrodes by simultaneously adding nickel and molybdenum sources suffer from overlapping catalytic active sites, which directly reduces catalytic efficiency and thus limits the large-scale promotion and application of molybdenum-doped nickel phosphide electrodes in water electrolysis hydrogen production technology.

[0040] In view of the problems existing in the prior art, the present invention provides a preparation method of a molybdenum-doped nickel phosphide electrode, comprising the following steps: dissolving a soluble nickel salt, ammonium fluoride and urea in water to obtain a mixed solution; wherein the molar ratio of the soluble nickel salt, ammonium fluoride and urea is 0.5-1.5:4:5; immersing a foamed metal in the mixed solution and performing a hydrothermal reaction to obtain a precursor Ni(CO3)OH / NF; during the hydrothermal reaction, urea and water are thermally decomposed to generate ammonia water to make the mixed solution weakly alkaline, and at the same time, urea is thermally decomposed to obtain carbonate ions; under weakly alkaline conditions, ammonium fluoride is used as a directing agent, and under the guiding effect of the ammonium fluoride, nickel ions react with carbonate ions and hydroxide ions in the mixed solution to generate basic nickel carbonate, which is attached to the foamed metal, and F -Embedded into the layered structure of basic nickel carbonate to obtain Ni(CO3)OH / NF; the precursor Ni(CO3)OH / NF is immersed in a molybdenum salt solution and subjected to a solvothermal reaction. During the solvothermal reaction, molybdenum ions diffuse into the Ni(CO3)OH / NF and replace some nickel atoms to obtain Mo-Ni(OH)2 / NF; Mo-Ni(OH)2 / NF and a phosphorus source are placed at the upper and lower ends of a muffle furnace respectively, and a high-temperature phosphating reaction is carried out in an inert atmosphere to obtain a molybdenum-doped nickel phosphide electrode.

[0041] The present invention adopts a step-by-step doping method to uniformly dope molybdenum atoms into the nickel lattice, effectively avoiding the problem of overlapping and stacking of molybdenum catalyst points and nickel catalytic sites caused by the simultaneous addition of nickel and molybdenum sources in the prior art, and effectively improving the catalytic efficiency of the molybdenum-doped nickel phosphide electrode.

[0042] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] A method for preparing a molybdenum-doped nickel phosphide electrode comprises the following steps:

[0045] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution.

[0046] S2. Immerse 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 100° C. for 6 h to obtain the precursor Ni(CO 3 )OH / NF.

[0047] S3. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.4 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 140°C for 6 h to obtain Mo-Ni(OH)2 / NF, which was recorded as 0.4Mo-Ni(OH)2 / NF.

[0048] S4. After placing Mo-Ni(OH)2 / NF and 1 g of sodium hypophosphite at the lower and upper ends of a muffle furnace, respectively, the muffle furnace was heated to 350°C at a heating rate of 2°C / min, maintained under an argon flow for 2 h, and then cooled to room temperature to obtain a Mo-NiP / NF electrode, recorded as 0.4Mo-NiP / NF.

[0049] Example 2

[0050] A method for preparing a molybdenum-doped nickel phosphide electrode is the same as the preparation steps in Example 1, except that the amount of Na2MoO4·2H2O in S2 is replaced from 0.24 mmol to 0.2 mmol, and the mass of sodium hypophosphite in S3 is replaced from 1 g to 0.2 g, comprising the following steps:

[0051] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution.

[0052] S2. Immerse 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 100° C. for 6 h to obtain the precursor Ni(CO 3 )OH / NF.

[0053] S3. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.2 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 140°C for 6 h to obtain Mo-Ni(OH)2 / NF, which was recorded as 0.2Mo-Ni(OH)2 / NF.

[0054] S4. After placing Mo-Ni(OH)2 / NF and 0.2 g of sodium hypophosphite at the lower and upper ends of a muffle furnace, respectively, the muffle furnace was heated to 350°C at a heating rate of 2°C / min, maintained under an argon flow for 2 h, and then cooled to room temperature to obtain a Mo-NiP / NF electrode, recorded as 0.2Mo-NiP / NF.

[0055] Example 3

[0056] A method for preparing a molybdenum-doped nickel phosphide electrode is the same as the preparation steps in Example 1, except that the amount of Na2MoO4·2H2O in S2 is replaced from 0.4 mmol to 0.6 mmol, and the mass of sodium hypophosphite in S3 is replaced from 1 g to 0.6 g, comprising the following steps:

[0057] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution; immerse a 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 100 ° C for 6 h to obtain the precursor Ni(CO3)OH / NF.

[0058] S2. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.6 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 140°C for 6 h to obtain Mo-Ni(OH)2 / NF, which was recorded as 0.6Mo-Ni(OH)2 / NF.

[0059] S3. After placing Mo-Ni(OH)2 / NF and 0.6 g of sodium hypophosphite at the lower and upper ends of a muffle furnace, respectively, the muffle furnace was heated to 350°C at a heating rate of 2°C / min, maintained under an argon flow for 2 h, and then cooled to room temperature to obtain a Mo-NiP / NF electrode, recorded as 0.6Mo-NiP / NF.

[0060] Example 4

[0061] A method for preparing a molybdenum-doped nickel phosphide electrode is the same as the preparation steps in Example 1, except that the amount of Na2MoO4·2H2O in S2 is replaced from 0.4 mmol to 0.8 mmol, and the mass of sodium hypophosphite in S3 is replaced from 1 g to 0.8 g, comprising the following steps:

[0062] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution.

[0063] S2. Immerse 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 100° C. for 6 h to obtain the precursor Ni(CO 3 )OH / NF.

[0064] S3. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.8 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 140°C for 6 h to obtain Mo-Ni(OH)2 / NF, which was recorded as 0.8Mo-Ni(OH)2 / NF.

[0065] S4. After placing Mo-Ni(OH)2 / NF and 0.8 g of sodium hypophosphite at the lower and upper ends of a muffle furnace, respectively, the muffle furnace was heated to 350°C at a heating rate of 2°C / min, maintained under an argon flow for 2 h, and then cooled to room temperature to obtain a Mo-NiP / NF electrode, recorded as 0.8Mo-NiP / NF.

[0066] Example 5

[0067] A method for preparing a molybdenum-doped nickel phosphide electrode comprises the following steps:

[0068] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution.

[0069] S2. Immerse 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 90° C. for 5 h to obtain the precursor Ni(CO 3 )OH / NF.

[0070] S3. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.4 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the inner lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 120°C for 8 h to obtain Mo-Ni(OH)2 / NF.

[0071] S4. Place Mo-Ni(OH)2 / NF and 1 g of sodium hypophosphite at the lower and upper ends of a muffle furnace, respectively. Heat the muffle furnace to 250°C at a heating rate of 2°C / min, maintain it under an argon flow for 3 hours, and then cool it to room temperature to obtain a Mo-NiP / NF electrode.

[0072] Example 6

[0073] A method for preparing a molybdenum-doped nickel phosphide electrode comprises the following steps:

[0074] S1. Dissolve 0.9683 g of nickel nitrate hexahydrate, 0.4937 g of ammonium fluoride, and 1.0008 g of urea in 60 mL of deionized water to obtain a mixed solution.

[0075] S2. Immerse 1 cm × 3 cm nickel foam in the mixed solution, then place the mixed solution in a reactor and perform a hydrothermal reaction at 150° C. for 8 h to obtain the precursor Ni(CO 3 )OH / NF.

[0076] S3. The precursor Ni(CO3)OH / NF was immersed in an aqueous solution consisting of 0.4 mmol of Na2MoO4·2H2O and 30 mL of ionized water, and then transferred to the inner lining of a reactor with a capacity of 100 mL. The solvent thermal reaction was carried out in an oven at 140°C for 6 h to obtain Mo-Ni(OH)2 / NF.

[0077] S4. After placing Mo-Ni(OH)2 / NF and 1 g of sodium hypophosphite at the lower and upper ends of a muffle furnace respectively, the muffle furnace was heated to 350°C at a heating rate of 2°C / min, maintained under an argon flow for 1 hour, and then cooled to room temperature to obtain a Mo-NiP / NF electrode.

[0078] observe Figure 1 From Figures (a) and (b) in the figure, it can be seen that the 0.8Mo-NiP / NF electrode exhibits three-dimensional structural characteristics, with numerous and uniform cavities distributed on its surface, which provides abundant sites for the attachment of molybdenum-doped nickel phosphide, and also means that the 0.8Mo-NiP / NF electrode has a large specific surface area. Figure 1 Figure (a) shows raised molybdenum-doped nickel phosphide particles with a diameter of approximately 2 μm attached to the surface of the 0.8Mo-NiP / NF electrode. This is due to the size effect of molybdenum ions during the high-temperature phosphating reaction. The presence of these particles not only significantly increases the specific surface area of ​​the 0.8Mo-NiP / NF electrode, but also increases the number of active sites, contributing to the overall performance of the 0.8Mo-NiP / NF electrode.

[0079] Depend on Figure 1 In Figure (b), a large number of uniform burr-like structures are observed on the surface of the nickel foam. This feature further expands the specific surface area of ​​the 0.8Mo-NiP / NF electrode. The larger specific surface area has a positive effect on improving the overall performance of the 0.8Mo-NiP / NF electrode. Furthermore, the increase in surface cavities also has a significant impact on the performance of the 0.8Mo-NiP / NF electrode. First, the increase in cavities improves the adsorption capacity of the 0.8Mo-NiP / NF electrode, resulting in better performance during adsorption and separation processes. Second, this porous structure helps reduce the weight of the 0.8Mo-NiP / NF electrode, which is of great significance for reducing device weight, reducing energy consumption, and improving the performance of the 0.8Mo-NiP / NF electrode. Furthermore, the presence of cavities helps provide more active sites, thereby enhancing the catalytic activity of the 0.8Mo-NiP / NF electrode, which has a significant impact on the catalytic oxidation, reduction, and decomposition reactions.

[0080] observe Figure 2 It was found that two significant and sharp diffraction peaks can be seen at 44.8° and 52.3°, which are attributed to the metallic nickel component in the Ni(CO3)OH / NF foam. In addition, Ni(CO3)OH / NF exhibits distinct diffraction peaks at 19.4°, 33.1°, 39.1°, 52.1°, 59.2°, and 621°. After comparing these diffraction peaks with the standard card Ni(OH)2 (PDF#14-0117), it was confirmed that these diffraction peaks correspond to the (001), (100), (101), (001), and (102) crystal planes of Ni(OH)2, respectively.

[0081] observe Figure 3It was found that Mo-Ni(OH)2 / NF showed significant diffraction peaks at 9.2°, 33.1°, 39.1°, 52.1°, 59.2°, and 62.1°. After comparing these diffraction peaks with the standard card Ni(OH)2 (PDF#14-0117), it was confirmed that these diffraction peaks corresponded to the (001), (100), (101), and (102) crystal planes of Ni(OH)2, respectively. Figure 2 and Figure 3 The XRD spectrum shows that the diffraction peak intensities and positions remain highly consistent, which indicates that the doping of molybdenum does not significantly change the crystal structure of Ni(OH)2.

[0082] observe Figure 4 It was concluded that characteristic peaks of Ni(OH)2 and NiO were generated in the Mo-NiP / NF electrode. After high-temperature phosphating reaction, the diffraction peak of MoNiP8 appeared in the XRD spectrum. The formation of NiO is attributed to the chemical reaction between Ni and oxygen in the air under high temperature conditions. Further, in an environment containing a small amount of PH3 gas, NiO will be converted into Ni3P, but due to the relative lack of phosphorus content, only Ni3P is formed. Among them, the diffraction peak intensity of metallic nickel in nickel foam is significant, which masks other diffraction peaks with lower crystallinity. In the XRD spectrum, there are several more prominent diffraction peaks, located at approximately 40.1°, 44.2°, 54.2°, and 66.2°, respectively. By comparing with the standard card PDF#50-1191, it was confirmed that these diffraction peaks correspond to the (110), (201), (210), (210) and (310) crystal planes of MoNiP8, respectively, Figure 4 The XRD patterns are consistent with the results obtained in the previous analysis. Furthermore, some unlabeled diffraction peaks are present in the XRD patterns, which also correspond to the crystal planes of MoNiP8 (PDF#50-1191). These additional diffraction peaks are due to the formation of a specific molybdenum-nickel-phosphorus compound structure during the high-temperature phosphating reaction.

[0083] at the same time, Figure 4 The diffraction peaks in the Ni(CO3)OH / NF exhibited a slight shift, which was attributed to the successful incorporation of molybdenum into the nickel foam matrix. XRD testing confirmed that the present invention successfully prepared a molybdenum-doped nickel phosphide electrode composed of Ni(CO3)OH / NF and MoNiP8.

[0084] observe Figure 5 Figure (a) shows that under the same current density conditions, compared with Ni(CO3)OH / NF and Mo-Ni(OH) 2 / NF, the 0.8Mo-NiP / NF electrode prepared in Example 4 exhibits a lower hydrogen evolution overpotential. Specifically, when the current density of the working electrode reaches 100 mA / cm 2 The Mo-NiP / NF electrode only needs an overpotential of 278mV. This is because the dense and fine burr structure formed on the surface of the Mo-NiP / NF electrode after the high-temperature phosphating reaction greatly increases the number of electron attachment sites and the effective reaction area, making the Mo-NiP / NF electrode more efficient than the Mo-Ni(OH) 2 / NF and Ni(CO3)OH / NF showed more outstanding performance in electrocatalytic hydrogen evolution. In addition, the size of the arc in the impedance diagram reflects the impedance of the electrochemical process. That is, the smaller the impedance arc, the smaller the impedance of the electrode to the electrochemical process, the greater the current density of the electrode in the electrochemical process, and the higher its catalytic activity. Figure 5 As shown in Figure (b), the Mo-NiP / NF electrode is better than Mo-Ni(OH) 2 / NF has better catalytic activity.

[0085] from Figure 6 (a) shows that the electrode catalytic hydrogen evolution overpotential changes with the change of molybdenum doping amount. Among them, the 0.6Mo-Ni(OH)2 / NF electrode has a smaller hydrogen evolution overpotential at the same current density. Similarly, it is observed that Figure 6 (b) shows that the semicircle diameters of Ni(CO3)OH / NF and 0.2Mo-Ni(OH)2 / NF are larger, indicating higher charge transfer resistances and poorer electrical conductivity for 0.2Mo-Ni(OH)2 / NF, indicating slower electron transport during the reaction, leading to poor electrochemical hydrogen evolution performance. 0.2Mo-Ni(OH)2 / NF is only slightly higher than Ni(CO3)OH / NF, primarily due to limited doping between molybdenum ions and the nickel precursor, which did not improve the defects of the original nickel precursor, such as the small number of active sites and poor electrical conductivity in the nickel foam. Furthermore, the redox current and redox peak of Mo-Ni(OH)2 / NF increase with increasing molybdenum ion concentration, indicating that the electrochemical performance of Mo-Ni(OH)2 / NF improves with increasing molybdenum ion concentration.

[0086] from Figure 7 (a) shows that the Mo doping amount has an important influence on the catalytic hydrogen evolution performance of the Mo-NiP / NF electrode. At the same current density, the smaller the overpotential, the better the catalytic hydrogen evolution performance of the electrode. Therefore, the 0.8Mo-NiP / NF electrode exhibits the best catalytic hydrogen evolution performance. Figure 5 and Figure 6Performance analysis shows that Mo doping significantly improves the catalytic performance of the catalytic electrode. Figure 7 Figure (b) shows that as the Mo doping concentration increases, the Nyquist semicircle diameter decreases significantly with increasing phosphorus concentration, indicating that its conductivity and catalytic activity gradually increase. This shows that molybdenum ion doping helps improve the kinetics of the electrode reaction, giving the Mo-NiP / NF electrode more outstanding electrochemical performance.

[0087] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Claims

1. A method for preparing a molybdenum-doped nickel phosphide electrode, characterized in that: The following steps are involved: Dissolving a soluble nickel salt, ammonium fluoride, and urea in water to obtain a mixed solution; wherein the molar ratio of the soluble nickel salt, ammonium fluoride, and urea is 0.5-1.5:4:5; The foam metal is immersed in the mixed solution and subjected to a hydrothermal reaction. In the hydrothermal reaction, urea and water are thermally decomposed to generate ammonia water, making the mixed solution weakly alkaline. At the same time, urea is thermally decomposed to generate carbonate ions. Under weak alkaline conditions, ammonium fluoride is used as a directing agent. Under the guiding effect of ammonium fluoride, nickel ions react with carbonate ions and hydroxide ions in the mixed solution to generate basic nickel carbonate, which is attached to the foam metal. - It is embedded into the layered structure of basic nickel carbonate to obtain the precursor Ni(CO3)OH / NF; The precursor Ni(CO3)OH / NF is immersed in a molybdenum salt solution and subjected to a solvothermal reaction. During the solvothermal reaction, molybdenum ions diffuse into the Ni(CO3)OH / NF and replace some nickel atoms to obtain Mo-Ni(OH)2 / NF. The Mo-Ni(OH)2 / NF and phosphorus source were placed at the upper and lower ends of a muffle furnace, respectively, and a high-temperature phosphating reaction was carried out in an inert atmosphere to obtain a molybdenum-doped nickel phosphide electrode. The conditions of the hydrothermal reaction are: hydrothermal reaction at 90℃~150℃ for 5h~8h; The conditions of the solvent thermal reaction are: reaction at 120℃~140℃ for 6h~8h.

2. The method for preparing a molybdenum-doped nickel phosphide electrode according to claim 1, characterized in that: The concentration of molybdenum ions in the molybdenum salt solution is 0.2mmol / L~0.8mmol / L.

3. The method for preparing a molybdenum-doped nickel phosphide electrode according to claim 1, characterized in that: The conditions for high temperature phosphating reaction are: phosphating at 250℃~350℃ for 1h~3h.

4. The method for preparing a molybdenum-doped nickel phosphide electrode according to claim 1, characterized in that: The mass ratio of Mo-Ni(OH)2 / NF to phosphorus source is 1:3~10.

5. The method for preparing a molybdenum-doped nickel phosphide electrode according to claim 1, characterized in that: The metal foam is selected from nickel foam, titanium foam or copper foam.

6. A molybdenum-doped nickel phosphide electrode obtained by the preparation method according to any one of claims 1 to 5.

7. The molybdenum-doped nickel phosphide electrode according to claim 6, characterized in that: In molybdenum-doped nickel phosphide electrodes, molybdenum atoms are doped into the lattice of nickel atoms.

8. Use of the molybdenum-doped nickel phosphide electrode according to claim 6 in preparing a negative electrode for hydrogen production by water electrolysis.

Images