A phosphide nanorarray catalyst for hydrogen evolution from seawater and a preparation method and application thereof

Abstract

The application discloses a phosphide nanometer array catalyst for seawater hydrogen evolution and a preparation method and application thereof. The catalyst takes foamed nickel as a carrier to provide support and conductive effect for the catalyst; the catalyst is composed of a composite material of nickel, molybdenum, phosphorus and cobalt, and a nanorod array structure of the catalyst main body is formed on the base. The cobalt-doped nickel molybdenum phosphide nanorod array catalyst provides high active sites, the phosphide layer is in-situ oxidized into an active phase of Ni(OH)2 to accelerate reaction kinetics, and granular phosphide (P-Metal bond) on the surface of the nanorod blocks Cl ‑ erosion, and a three-dimensional porous structure promotes bubble detachment to resist seawater corrosion; the catalyst can simultaneously serve as a cathode (HER) and an anode (OER) to realize dual-function integration, realizes full-hydrolysis voltage ≤1.60 V (10 mA cm ‑2 ) in 1 M KOH solution, and stably operates for ≥88 h (current density attenuation rate ≤10%) under a cell voltage of 1.90 V.

Description

[0001] Technical Field This invention belongs to the field of catalyst preparation technology, specifically a phosphide nanoarray catalyst for hydrogen evolution in seawater, its preparation method, and its application. Background Technology

[0002] With the escalating global energy crisis, hydrogen energy, as a clean and efficient secondary energy source, has attracted widespread attention. Seawater electrolysis for hydrogen production, as a cutting-edge method, can effectively couple the utilization of renewable energy sources (such as wind and solar power) from deep-sea areas to produce renewable hydrogen (green hydrogen), achieving near-zero carbon emissions. It is an effective way to efficiently convert and store intermittent energy sources.

[0003] Hydrogen production through seawater electrolysis requires highly active and stable electrocatalysts to catalyze the water electrolysis reaction, reduce the reaction overpotential, and thus improve hydrogen production efficiency. The catalysts to be developed include hydrogen evolution catalysts for the cathode hydrogen evolution reaction and oxygen evolution catalysts for the anode oxygen evolution reaction. Currently, commercially available catalysts are mainly noble metal catalysts (HER: Pt / C; OER: RuO2 or IrO2). However, the scarcity and high cost of noble metals hinder their large-scale application in the field of water electrolysis. Therefore, the design and synthesis of non-noble metal electrocatalysts for water electrolysis has significant scientific and practical implications.

[0004] Transition metal doping has attracted much attention as a catalyst synthesis strategy to enhance conductivity and catalytic activity. Phosphating can alter the ionic valence state and microstructure of materials, generating layered structures and increasing the electrochemical surface area. Furthermore, phosphorus can effectively bind to reaction intermediates, increasing the proton acceptor sites and enhancing the activity of the catalyst after phosphating. The polymetallic phosphides prepared by this technique exhibit diverse compositions and have the potential advantage of enhanced catalytic activity. A particulate cobalt-doped nickel-molybdenum phosphide nanorod array catalyst was designed and developed on a nickel foam substrate using transition metal doping and phosphating strategies. This constructed a stable and efficient seawater electrolysis hydrogen production system using non-precious metal hydrogen evolution catalysts, potentially addressing the key issue of scarce freshwater resources. Summary of the Invention

[0005] The purpose of this invention is to address several challenges in seawater electrolysis for hydrogen production, including the high cost and scarcity of precious metal catalysts, ion corrosion and stability issues during seawater electrolysis, and the synergistic enhancement mechanism of phosphating and cobalt doping. This invention provides a phosphide nanoarray catalyst for seawater hydrogen evolution and its preparation method. Combining a "hydrothermal reaction—cobalt doping—phosphating" catalyst preparation strategy, this invention innovatively employs a cobalt doping strategy to enhance conductivity and catalytic activity. The phosphating process alters the microstructure and valence state of the material, and the design of a nanorod array structure increases the specific surface area, enabling the catalyst to achieve continuous seawater cathode hydrogen production under low potential, high current density, and stable and efficient conditions.

[0006] This invention also provides an application of a phosphide nanoarray catalyst for hydrogen evolution in seawater. The non-precious metal-based seawater electrolysis hydrogen production system is a system driven by renewable energy, comprising two main parts: electrolytic hydrogen evolution and oxygen evolution. In this system, a cobalt-doped nickel-molybdenum phosphide nanorod array catalyst provides highly active sites (Mo sites optimized by Co doping), and the in-situ oxidation of the phosphide layer to the Ni(OH)2 active phase accelerates the reaction kinetics; the particulate phosphide (P-Metal bonds) on the nanorod surface blocks Cl... - Erosion resistance; the three-dimensional porous structure promotes bubble desorption and resists seawater corrosion; the same catalyst simultaneously serves as both cathode (HER) and anode (OER), achieving dual-function integration. Key bottlenecks in clean energy conversion are addressed through the design of novel catalysts.

[0007] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows: A phosphide nanoarray catalyst for hydrogen evolution in seawater is proposed. The catalyst uses nickel foam as a substrate, grows a cobalt-doped nickel-molybdenum oxide precursor, and then phosphates it to form a catalyst with the chemical formula (MoNi). 1-X Co X The active phase of P is a two-phase coexistence structure with Ni2P as the main phase and incompletely phosphated NiMoO4 as the secondary phase.

[0008] Furthermore, in this catalyst, based on nickel-molybdenum phosphide (NiMoP), the electronic structure is optimized through cobalt doping, while retaining some unphosphated molybdate to improve conductivity; a vertical nanorod array (diameter ≈100 nm) is constructed on a nickel foam substrate, and the surface is modified with a particulate rough layer to increase the electrochemically active area (ECSA) to ≥180 mF cm⁻¹. -2 (250 times better than smooth surfaces); the gaps between nanorods promote bubble desorption, and the phosphating layer (P-Metal bonds) forms a physical barrier to resist Cl. - Corrosion-resistant and stable. Finally, it achieves low-cost and stable operation in practical applications. When used as an anode and cathode, the total hydrolysis voltage needs to be ≤1.60 V (current density 10 mA cm⁻¹). -2 It maintains stability for >88 h at 1.90 V (current decay rate <5%), achieving compatibility with seawater hydrogen production.

[0009] Furthermore, this invention also protects a method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, comprising the following steps: (1) Preparation of nickel-molybdenum foam nickel catalytic precursor I: First, the nickel foam is ultrasonically treated in solvent A and solvent B in sequence to remove surface organic matter and impurities; then it is annealed at a certain temperature and under a protective atmosphere to completely reduce the surface oxide layer and obtain reduced nickel foam. Weigh out nickel salt and molybdate, dissolve them in solvent C, and stir continuously until they are completely dissolved to obtain solution I; The reduced nickel foam and solution I were transferred to a Teflon-lined stainless steel autoclave for reaction. After the reaction was completed, precursor I was obtained. After the precursor I was naturally cooled to room temperature, it was washed alternately with solvent C and solvent B. Then the washed precursor I was placed in a vacuum oven to dry for later use. (2) Synthesis of cobalt-doped nickel-molybdenum catalytic precursor II: Reagent A is dispersed in solvent B to obtain solution II; at the same time, cobalt salt is dissolved in solvent D to obtain solution III; then solutions II and III are stirred and mixed evenly to obtain a mixed solution; the dried precursor I is vertically immersed in the mixed solution to carry out the reaction. After the reaction is complete, precursor II is obtained. Precursor II is washed with solvent D and then dried for later use. (3) Cobalt-doped nickel-molybdenum phosphide catalyst ((NiMo)1) x Co x Preparation of P / NF: Reagent B was weighed and placed upstream of the quartz boat, and the dried precursor II was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, and the protective atmosphere B was maintained. The tube furnace was heated to react and then cooled to room temperature to obtain a cobalt-doped nickel-molybdenum phosphide catalyst, which is the desired phosphide nanoarray catalyst for hydrogen evolution in seawater.

[0010] Preferably, in the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, solvent A, solvent B, solvent C and solvent D are each selected from at least one of deionized water, anhydrous ethanol, anhydrous methanol and acetone.

[0011] Preferably, in the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, reagent A is selected from at least one of 2-methylimidazole and red phosphorus; reagent B is selected from at least one of 2-methylimidazole, red phosphorus, sulfur, and sodium thiosulfate.

[0012] Preferably, in the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the precursor I is selected from NiMoO4 / NF, (NiMo)1 x Co x At least one of O4 / NF; precursor II is selected from NiMoO4 / NF, (NiMo)1 x Co xAt least one of O4 / NF.

[0013] Preferably, in step (1) of the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the annealing temperature is 400~500℃, the annealing time is 0.5~1.5 hours, more preferably 1 hour; the protective atmosphere is a mixed atmosphere, which contains 5%~10% protective gas A and 90%~95% protective gas B by volume percentage; the protective gas A contains at least one of argon and hydrogen, and the protective gas B contains at least one of argon and hydrogen; the gas pressure of the protective atmosphere is 1.5~2.0 Torr.

[0014] Preferably, in step (1) of the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the area of ​​the nickel foam is 1 cm × 1.5 cm; the volume ratio of nickel foam to solvent A is arbitrary; and the volume ratio of nickel foam to solvent B is arbitrary.

[0015] Preferably, in step (1) of the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the molar ratio of nickel salt to molybdate is 1:1 to 1:4; the ratio of the amount of nickel salt (mmol) to the volume of solvent C (mL) is 1:15; the ratio of the amount of reduced nickel foam to the volume of solution I (mL) is 1:25; the reaction temperature in the Teflon-lined stainless steel autoclave is 160 to 200°C, and the reaction time is 6 to 10 hours; the washing is performed alternately with solvent C and solvent B three times each; and the temperature in the vacuum oven is 60°C.

[0016] Preferably, in step (2) of the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the ratio of the amount of reagent A (mmol) to the volume of solvent B (mL) is 1:25 to 4:25; the ratio of the amount of cobalt salt (mmol) to the volume of solvent D (mL) is 0.20 to 1:25; the reaction time immersed in the mixed solution is 24 hours; and the number of times the solution is washed with solvent D is 3.

[0017] Preferably, in step (3) of the method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the amount of reagent B added is 1–30 mg / cm³. 2 (Doping amount per unit area of ​​catalyst). The gas pressure of the protective gas B atmosphere is 1.5 Torr, and protective gas B contains at least one of argon and hydrogen; the heating rate of the tube furnace reaction is 2℃ / min. 1 The temperature was raised to 500℃ and the reaction time was maintained for 90-120 minutes.

[0018] Furthermore, this invention also protects a phosphide nanoarray catalyst for hydrogen evolution in seawater that can be prepared using any of the methods or combinations of method steps described above. This catalyst is a particulate cobalt-doped nickel-molybdenum phosphide nanorod array catalyst with highly efficient bifunctional catalytic activity. The cathode requirement is that the proton reduction reaction (HER) is triggered in an alkaline environment, i.e., HER: 2H₂O + 2e⁻. →H2+2OH Anode requirement: Catalytic oxygen evolution reaction, i.e., OER: 4OH →O2 + 2H2O + 4e .

[0019] Furthermore, in the phosphide nanoarray catalyst for hydrogen evolution in seawater prepared above, the cobalt doping amount is 0.5~2wt%.

[0020] Furthermore, this invention also protects the application of catalysts prepared by the above-described catalysts or methods in the hydrogen evolution of seawater.

[0021] A phosphide nanoarray catalyst for hydrogen evolution in seawater, powered by renewable electricity, enables continuous hydrogen evolution reaction (HER) in the cathode region, achieving hydrogen production through electrolysis. The reaction formula is as follows: Cathode region: 2H₂O + 2e⁻ - →H₂↑+2OH - Anode region: 2H₂O - 4e - →O2↑+4H + Overall reaction: 2H₂O → 2H₂↑ + O₂↑ The measured potential must be converted to a relative standard reversible hydrogen electrode potential. According to the Nernst equation, the conversion formulas for the experiments in this chapter are as follows:

[0022] in E RHE This represents the relative standard reversible hydrogen electrode potential; E Hg / HgO It represents the measurement of electric potential.

[0023] The overpotential of the cathode HER reaction is:

[0024] The overpotential of the anodic OER reaction is:

[0025] The above synthesis yielded a particulate cobalt-doped nickel-molybdenum phosphide nanorod array catalyst, which was applied to seawater electrolysis for hydrogen production. As a stable and efficient non-precious metal hydrogen evolution catalyst for seawater, it provides a new research approach for further improving the catalytic performance of seawater hydrogen evolution catalysts.

[0026] This phosphide nanoarray catalyst for hydrogen evolution in seawater uses Ni-Mo-Co phosphide as a support. The dynamic conversion of phosphide / nickel oxide and the active phase of Ni2P→Ni(OH)2 in OER enable self-repair and support recycling mechanism, achieving corrosion resistance of the phosphide layer and stress resistance of the nanorod array.

[0027] Compared with the prior art, the main advantages of the present invention are as follows: (1) This invention creatively synthesizes (NiMo)1 through three steps: hydrothermal reaction, cobalt doping, and phosphating. x Co x The P / NF catalyst has a rich array of nanorods growing on its surface. The nanorods exhibit a unique rough granular morphology, which increases the electrochemical active surface area and forms more catalytic active sites.

[0028] (2) Characterization analysis revealed that the main components of the catalyst are Ni2P and NiMoO4. Furthermore, simulation calculations verified the promoting effect of cobalt doping on the catalytic hydrogen evolution performance; during oxygen evolution, NiO is generated on the catalyst surface. Characterization analysis successfully verified that it is the catalytic active site for the oxygen evolution reaction. Further testing of this catalyst as both hydrogen evolution and oxygen evolution electrodes in water electrolysis also demonstrated excellent catalytic activity and stability, suggesting the potential for a highly efficient, stable, and low-cost seawater hydrogen evolution catalyst.

[0029] (3) This catalyst has excellent catalytic performance and stability in alkaline seawater, which solves the problems of low hydrogen production efficiency and severe corrosion of seawater impurity ions in existing seawater electrolysis technology, realizes the efficient utilization of clean energy and green chemical production, and can be effectively applied to seawater electrolysis hydrogen production.

[0030] (4) This catalyst uses nickel foam as a support to provide support and conductivity. It is a composite material composed of nickel, molybdenum, phosphorus and cobalt. The catalyst body forms a nanorod array structure on the substrate. The surface of the nanorods has a rough granular morphology to increase the electrochemical active surface area and the number of catalytic active sites.

[0031] (5) The catalyst is a nano-array seawater hydrogen evolution catalyst with high efficiency catalytic performance. It can significantly reduce the hydrogen evolution overpotential and improve the efficiency of hydrogen production by water electrolysis. The catalyst shows good stability in alkaline fresh water and alkaline seawater and is suitable for different water electrolysis environments.

[0032] (6) The catalyst has been treated with cobalt doping and phosphorus phosphating, which optimizes the structure and performance of the catalyst and improves its activity and stability. Attached Figure Description

[0033] Figure 1 This invention relates to a phosphide nanoarray catalyst ((NiMo)1) for hydrogen evolution in seawater. x Co x A schematic diagram of the synthesis of P / NF; Figure 2 (NiMo)1 x Co x Scanning electron microscope image of P / NF; Figure 3 (NiMo)1 x Co x Hydrogen evolution polarization curves and constant current stability test graphs of P / NF; Figure 4 (NiMo)1 x Co x Oxygen evolution polarization curves and constant current stability test results for P / NF. Detailed Implementation

[0034] A method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, the method comprising the following steps: 1. Preparation of nickel-molybdenum foam nickel catalytic precursor (NiMoO4 / NF) catalysis.

[0035] First, cut the nickel foam and sonicate it in solvents A and B for 30 minutes each to remove surface organic matter and impurities. Then, anneal it at 500°C for one hour in a protective atmosphere (volume ratio: 10% protective gas A: 90% protective gas B; gas pressure: 1.5 Torr) to completely reduce the surface oxide layer. Weigh 1 mmol of NiCl2·6H2O and 1 mmol of Na2MoO4·2H2O and dissolve them in 15 mL of solvent C, stirring continuously until completely dissolved. Transfer the reduced nickel foam and solution to a 50 mL Teflon-lined stainless steel autoclave and react at 160°C for 6 hours. After naturally cooling to room temperature, remove the precursor NiMoO4 / NF and wash it three times alternately with solvents C and B. Then, dry NiMoO4 / NF in a vacuum oven at 60°C for later use.

[0036] Cobalt-doped nickel-molybdenum catalytic precursor ((NiMo)1) x Co x Synthesis of NiMoO4 / NF. 4 mmol of 2-methylimidazole was dispersed in 25 mL of solvent B, while 1 mmol of Co(NO3)2·6H2O was dissolved in 25 mL of solvent D. The two solutions were then stirred and mixed thoroughly. NiMoO4 / NF was then vertically immersed in the mixed solution and reacted for 24 hours. After the reaction was complete, the precursor (NiMo)1 was removed. x Co x O4 / NF was washed three times with solvent D and then dried for later use.

[0037] 2. Cobalt-doped nickel-molybdenum phosphide ((NiMo)1) x Co x Preparation of P / NF. 20 mg of red phosphorus was weighed and placed upstream of a quartz boat, and the precursor (NiMo)1 was added. x Co x O4 / NF was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, maintaining a protective atmosphere of B (gas pressure: 1.5 Torr). The tube furnace was incubated at 2°C for 1 minute. 1 The heating rate was increased to 500℃, and the sample reaction was maintained for 90 minutes, followed by cooling to room temperature to obtain catalyst (NiMo)1. x Co x P / NF.

[0038] Furthermore, the cobalt doping content is 1%.

[0039] Furthermore, solvent A comprises one or more of deionized water, anhydrous ethanol, anhydrous methanol, and acetone; solvent B comprises one or more of deionized water, anhydrous ethanol, anhydrous methanol, and acetone; solvent C comprises one or more of deionized water, anhydrous ethanol, anhydrous methanol, and acetone; and solvent D comprises one or more of deionized water, anhydrous ethanol, anhydrous methanol, and acetone.

[0040] Furthermore, the protective gas A comprises one or more of argon and hydrogen; the protective gas B comprises one or more of argon and hydrogen.

[0041] Furthermore, the design requirements for cobalt-doped nickel-molybdenum phosphide nanorod array catalysts are as follows: using nickel foam as a substrate, a cobalt-doped nickel-molybdenum oxide precursor is grown, which is then phosphated to form the chemical formula (NiMo). 1-X Co X The active phase of P is a two-phase coexistence structure with Ni2P as the main phase and incompletely phosphated NiMoO4 as the secondary phase.

[0042] Furthermore, the design requirements for cobalt-doped nickel-molybdenum phosphide nanorod array catalysts are as follows: First, they must possess highly efficient bifunctional catalytic activity. The cathode requirement is that it must trigger the proton reduction reaction (HER: 2H₂O + 2e⁻) in an alkaline environment. →H2+2OH Anode requirements: Catalytic oxygen evolution reaction (OER: 4OH) →O2 + 2H2O + 4e Secondly, its composition and structure need to be synergistically optimized. Based on nickel-molybdenum phosphide (NiMoP), the electronic structure is optimized by cobalt doping, while retaining some unphosphated molybdate to improve conductivity; a vertical nanorod array (diameter ≈100 nm) is constructed on a nickel foam substrate, and a granular rough layer is modified on the surface to increase the electrochemically active area (ECSA) to ≥180 mF cm⁻¹. -2 (250 times better than smooth surfaces); the gaps between nanorods promote bubble desorption, and the phosphating layer (P-Metal bonds) forms a physical barrier to resist Cl. - Corrosion-hardened stability. Finally, it achieves low-cost, stable operation in system-level applications. When used as anode and cathode, the total hydrolysis voltage needs to be ≤1.60 V (current density 10 mA cm⁻¹), and it maintains stability for >88 h at 1.90 V (current decay rate <5%), achieving seawater hydrogen production compatibility.

[0043] Furthermore, the design requirements for cobalt-doped nickel-molybdenum phosphide nanorod array catalysts are as follows: using Ni-Mo-Co phosphide as a support, dynamic conversion of phosphide / nickel oxide, Ni2P→Ni(OH)2 active phase in OER, realizing self-healing support recycling mechanism, and achieving corrosion resistance of phosphide layer + stress resistance of nanorod array.

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention. Furthermore, it should be understood that after reading this invention, those skilled in the art can make various modifications and alterations to it, but these equivalent forms also fall within the scope defined by the appended claims.

[0045] In this application, all percentages not explicitly stated represent mass percentage content.

[0046] In this invention, some conventional operating equipment, devices and components have been omitted or only briefly described.

[0047] Example 1: Preparation of the nickel-molybdenum foam nickel catalytic precursor (NiMoO4 / NF): First, a piece of nickel foam with an area of ​​1 cm × 1.5 cm was cut and ultrasonically treated in acetone and ethanol solutions for 30 minutes each to remove surface organic matter and impurities. Then, it was annealed at 500℃ in an H2 / Ar mixed atmosphere (volume ratio: 10% H2: 90% Ar; gas pressure: 1.5 Torr) for one hour to completely reduce the surface oxide layer. 1 mmol of NiCl2·6H2O and 1 mmol of Na2MoO4·2H2O were weighed and dissolved in 15 ml of deionized water, and stirred continuously until completely dissolved. The reduced nickel foam and solution were transferred to a 50 ml Teflon-lined stainless steel autoclave and reacted at 160℃ for 6 hours. After naturally cooling to room temperature, precursor I NiMoO4 / NF was obtained. The precursor I NiMoO4 / NF was washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum oven at 60°C for later use.

[0048] Cobalt-doped nickel-molybdenum catalytic precursor ((NiMo)1) x Co x Synthesis of NiMoO4 / NF: 4 mmol of 2-methylimidazole was dispersed in 25 mL of anhydrous methanol to obtain solution II; simultaneously, 1 mmol of Co(NO3)2·6H2O was dissolved in 25 mL of anhydrous methanol to obtain solution III; then, solutions II and III were stirred and mixed thoroughly to obtain a mixed solution. The previously prepared precursor I, NiMoO4 / NF, was vertically immersed in the mixed solution and reacted for 24 hours. After the reaction was complete, precursor II (NiMo)1 was obtained. x Co x O4 / NF. Precursor II (NiMo)1 x Co x O4 / NF was washed three times with anhydrous methanol and then dried for later use.

[0049] Cobalt-doped nickel-molybdenum phosphide ((NiMo)1) x Co x Preparation of P / NF: Weigh 20 mg of red phosphorus and place it upstream of a quartz boat, then add precursor II (NiMo)1. x Co x O4 / NF was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, maintaining an argon atmosphere (gas pressure: 1.5 Torr). The tube furnace was heated to 2 °C per minute. 1The heating rate was increased to 500℃, and the sample reaction was maintained for 90 minutes, followed by cooling to room temperature to obtain the catalyst (NiMo1). x Co x P / NF (based on analysis, the catalyst is (NiMo) 0.66 Co 0.33 P / NF).

[0050] Electrochemical testing method for the catalyst: Electrochemical performance tests were conducted in 1M KOH solution using a high-power electrochemical workstation (Solartron 1260+1287, Solartron Metrology). The entire testing process was carried out at room temperature under either an argon (HER) or oxygen (OER) atmosphere. A three-electrode system was used: a carbon rod electrode as the counter electrode, an Hg / HgO electrode as the reference electrode, and the working electrode directly using the synthesized catalyst sample without the need for binders or conductive agents. The working electrode area was controlled to be 1×1 cm². 2 Before the formal electrochemical testing, cyclic voltammetry curves were continuously scanned on the catalyst sample (scan rate 100 mV s). 1 The process continues until the catalyst material stabilizes and the curve no longer fluctuates. The linear sweep voltammetry (LSV) scan range for HER is [missing information]. The scanning range for OER cyclic voltammetry (CV) is 1.0–1.8 V (vs. RHE), with a scan rate of 2 mV / s for both methods. The initial voltage is 0.6–0.1 V (vs. RHE). 1 To reduce the influence of capacitive current, solution impedance compensation was applied to all test curves. The measured potential must be converted to a relative standard reversible hydrogen electrode potential.

[0051] Example 2: (NiMo) 0.66 Co 0.33 SP / NF The preparation method is the same as in Example 1, except that: 10 mg of sulfur and 10 mg of red phosphorus are weighed and placed upstream of the quartz boat, and precursor II (NiMo) is added. 0.66 Co 0.33 O4 / NF was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, maintaining an argon atmosphere (gas pressure: 1.5 Torr). The tube furnace was heated to 2 °C per minute. 1 The heating rate was increased to 500℃, and the sample reaction was maintained for 90 minutes, followed by cooling to room temperature to obtain the catalyst (NiMo). 0.66 Co0.33 SP / NF.

[0052] Comparative Example 1: Catalyst NiMoO4 / NF The preparation method is the same as in Example 1, except that the precursor I NiMoO4 / NF is placed in a quartz boat. The quartz boat is then placed in a tube furnace, maintaining an argon atmosphere (gas pressure: 1.5 Torr). The tube furnace is heated to 2°C / min. 1 The heating rate was increased to 500℃, the sample reaction was maintained for 90 minutes, and then cooled to room temperature to obtain the catalyst NiMoO4 / NF.

[0053] Comparative Example 2: Catalyst NiMoP / NF The preparation method is the same as in Example 1, except that 20 mg of red phosphorus was weighed and placed upstream of the quartz boat, and the precursor I NiMoO4 / NF was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, maintaining an argon atmosphere (gas pressure: 1.5 Torr). The tube furnace was heated to 2°C / min. 1 The heating rate was increased to 500℃, the sample reaction was maintained for 90 minutes, and then cooled to room temperature to obtain the catalyst NiMoP / NF.

[0054] Comparative Example 3: Catalyst (NiMo) 1 x Co x O4 / NF The preparation method is the same as the nickel-molybdenum foam nickel catalytic precursor and cobalt-doped nickel-molybdenum catalytic precursor in Example 1. Precursor II (NiMo)1 x Co x O4 / NF was placed in a quartz boat. The quartz boat was then placed in a tube furnace, maintaining an argon atmosphere (gas pressure: 1.5 Torr). The tube furnace was heated to 2 °C per minute. 1 The heating rate was increased to 500℃, and the sample reaction was maintained for 90 minutes, followed by cooling to room temperature to obtain catalyst (NiMo)1. x Co x O4 / NF (the catalyst was determined to be (NiMo)). 0.66 Co 0.33 O4 / NF).

[0055] Comparative Example 4: Preparation of Pt / C / NF and RuO2 / NF catalysts Prepare a mixed solution of 50 μL Nafion, 450 μL anhydrous ethanol, and 500 μL deionized water. Weigh 10 mg of 20 wt.% Pt / C and RuO2 and dissolve them separately in their respective mixed solutions. Sonicate the solutions at room temperature for 30 minutes to form a catalyst ink. Evenly drop 300 μL of the ink onto reduced nickel foam and air dry at room temperature.

[0056] Nanoarray seawater hydrogen evolution catalyst exhibits excellent catalytic performance in alkaline seawater: through Figure 2 Scanning electron microscopy revealed that the catalyst morphology was a nanorod array structure. Figure 3 In alkaline seawater solutions: at 100 mA cm -2 At a current density of 196 mV, the hydrogen evolution overpotential is 196 mV, and it can maintain stable operation for more than 100 hours, demonstrating good hydrogen evolution stability in seawater. Figure 4 In alkaline seawater solutions: at 100 mA cm⁻¹ 2 At a given current density, the oxygen evolution overpotential is 474 mV. The constant current test can maintain operation for over 100 hours. After 100 hours of testing, the required overpotential of the catalyst shows a significant increase. (NiMo) 0.66 Co 0.33 The P / NF catalyst, acting as both cathode and anode, achieves a total hydrolysis voltage ≤1.60 V (10 mA cm⁻¹) in 1 M KOH solution. 2 It can operate stably for ≥88 h at a tank voltage of 1.90 V (current density decay rate ≤10%).

[0057] In summary, the catalyst of this invention is a cathode hydrogen evolution catalyst. In its preparation method, a particulate cobalt-doped nickel-molybdenum phosphide nanorod array catalyst is creatively introduced into the seawater electrolysis hydrogen production process. Co doping and phosphating significantly alter the ionic valence state and catalyst morphology, improving electrochemical activity and achieving continuous seawater electrolysis hydrogen production under low potential, high current density, and stable and efficient performance. Simultaneously, this invention also addresses the anodic oxygen evolution reaction, specifically targeting (NiMo)1... x Co x The P / NF catalyst was tested and showed excellent performance in alkaline fresh water. In alkaline seawater, the catalyst still maintained a certain degree of catalytic oxygen evolution activity and stability.

[0058] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0059] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A phosphide nanoarray catalyst for hydrogen evolution in seawater, characterized in that, This catalyst uses nickel foam as a substrate to grow a cobalt-doped nickel-molybdenum oxide precursor, which is then phosphated to form a catalyst with the chemical formula (MoNi). 1-x Co x The active phase of P is a two-phase coexistence structure with Ni2P as the main phase and incompletely phosphated NiMoO4 as the secondary phase.

2. A method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater, characterized in that, The method includes the following steps: (1) Preparation of nickel-molybdenum foam nickel catalytic precursor I: First, the nickel foam is ultrasonically treated in solvent A and solvent B in sequence to remove surface organic matter and impurities; then it is annealed at a certain temperature and under a protective atmosphere to completely reduce the surface oxide layer and obtain reduced nickel foam. Weigh out nickel salt and molybdate and dissolve them in solvent C. Stir continuously until they are completely dissolved to obtain solution I. The reduced nickel foam and solution I were transferred to a Teflon-lined stainless steel autoclave for reaction. After the reaction was completed, precursor I was obtained. After the precursor I was naturally cooled to room temperature, it was washed alternately with solvent C and solvent B. Then the washed precursor I was placed in a vacuum oven to dry for later use. (2) Synthesis of cobalt-doped nickel-molybdenum catalytic precursor II: Reagent A is dispersed in solvent B to obtain solution II; at the same time, cobalt salt is dissolved in solvent D to obtain solution III; then solutions II and III are stirred and mixed evenly to obtain a mixed solution; the dried precursor I is vertically immersed in the mixed solution to carry out the reaction. After the reaction is complete, precursor II is obtained. Precursor II is washed with solvent D and then dried for later use. (3) Preparation of cobalt-doped nickel-molybdenum phosphide catalysts: Reagent B was weighed and placed upstream of the quartz boat, and the dried precursor II was placed downstream of the quartz boat. The quartz boat was then placed in a tube furnace, and the protective atmosphere B was maintained. The tube furnace was heated to react and then cooled to room temperature to obtain a cobalt-doped nickel-molybdenum phosphide catalyst, which is the desired phosphide nanoarray catalyst for hydrogen evolution in seawater.

3. The method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 2, characterized in that: Solvents A, B, C, and D are each selected from at least one of deionized water, anhydrous ethanol, anhydrous methanol, and acetone; reagent A is selected from at least one of 2-methylimidazole and red phosphorus; reagent B is selected from at least one of 2-methylimidazole, red phosphorus, sulfur, and sodium thiosulfate; and precursor I is selected from NiMoO4 / NF and (NiMo)1. x Co x At least one of O4 / NF; precursor II is selected from NiMoO4 / NF, (NiMo)1 x Co x At least one of O4 / NF.

4. The method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 2, characterized in that: In step (1), the annealing temperature is 400~500℃, and the annealing time is 0.5~1.5 hours; the protective atmosphere is a mixed atmosphere, which contains 5%~10% protective gas A and 90%~95% protective gas B by volume percentage; the protective gas A contains at least one of argon and hydrogen, and the protective gas B contains at least one of argon and hydrogen; the gas pressure of the protective atmosphere is 1.5~2.0 Torr; the molar ratio of nickel salt to molybdate is 1:1~1:4; the ratio of the amount of nickel salt (mmol) to the volume of solvent C (mL) is 1:15; the ratio of the amount of reduced nickel foam to the volume of solution I (mL) is 1:25; the reaction temperature in the Teflon-lined stainless steel autoclave is 160~200℃, and the reaction time is 6~10 hours; the number of times the solvent C and solvent B are used for alternating cleaning is 3 times each; the temperature in the vacuum oven is 60℃.

5. The method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 2, characterized in that: In step (2), the ratio of the amount of reagent A (mmol) to the volume of solvent B (mL) is 1:25 to 4:25; the ratio of the amount of cobalt salt (mmol) to the volume of solvent D (mL) is 0:20 to 1:25; the reaction time in the mixed solution is 24 hours; and the number of times the solution is washed with solvent D is 3.

6. A method for preparing a phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 2, characterized in that: In step (3), the gas pressure of the protective gas B atmosphere is 1.5 Torr, and the protective gas B contains at least one of argon and hydrogen; the heating rate of the tube furnace reaction is 2℃ min. 1 The temperature was raised to 500℃ and the reaction time was maintained for 90-120 minutes.

7. A phosphide nanoarray catalyst for hydrogen evolution in seawater prepared by any of the methods described in claims 2-10.

8. A phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 7, characterized in that, This catalyst possesses highly efficient bifunctional catalytic activity; the cathode requirement is that the proton reduction reaction, HER: 2H₂O + 2e⁻, be triggered in an alkaline environment. →H2+2OH Anode requirement: Catalytic oxygen evolution reaction, i.e., OER: 4OH →O2 + 2H2O + 4e .

9. A phosphide nanoarray catalyst for hydrogen evolution in seawater according to claim 7, characterized in that: The cobalt doping level is 0.5~2 wt%.

10. The application of the catalyst as described in claim 7 in hydrogen evolution from seawater.

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