A method for preparing and applying a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst.

Abstract

This invention relates to the field of electrocatalytic materials technology, specifically to a method for preparing and applying a polyoxoacid-etched optimized nickel molybdate oxygen evolution electrocatalyst. The preparation method includes the following steps: flower-shaped nickel molybdate nanorods, synthesized in situ on nickel foam using a one-step hydrothermal synthesis method, are etched in a mixed solution of ethanol, water, and polyoxoacids; washed; and dried to obtain the polyoxoacid-etched optimized nickel molybdate oxygen evolution electrocatalyst. This preparation method significantly improves the oxygen evolution reaction performance of the binary nickel-based nickel molybdate material, achieving highly efficient electrocatalysis of the oxygen evolution reaction while ensuring the stability of the catalytic material. The prepared polyoxoacid-etched optimized nickel molybdate oxygen evolution electrocatalyst can be directly used as a self-supporting electrode for electrocatalytic oxygen evolution reactions. The method is simple, environmentally friendly, low-cost, and has low production costs.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to a method for preparing and applying a multimetallic oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalytic material. Background Technology

[0002] Electrocatalytic water splitting (2H₂O → O₂ + 2H₂) is a highly efficient and sustainable method for hydrogen production, promising to address the energy crisis and environmental problems caused by traditional fossil fuels. The hydrogen evolution reaction (HER) is a two-electron-proton coupled reaction, while the oxygen evolution reaction (OER) is a four-electron-proton coupled reaction, requiring higher energy to overcome the energy barrier. Therefore, OER is generally considered the decisive step in water splitting, significantly reducing the efficiency of electrochemical water splitting. To overcome the influence of OER on the electrochemical water splitting process, selecting a suitable catalyst is crucial. Therefore, there is an urgent need to develop high-performance electrocatalysts to accelerate the kinetics of the oxygen evolution reaction.

[0003] Currently, noble metal oxides, such as RiO2 and RuO2, are the most widely used anode catalysts, but their high cost and low availability hinder their practical application. Transition metal oxides (TMOs) are low-cost, abundant, and possess good OER catalytic activity. Many research groups are developing them as alternatives to OER electrocatalysts, and optimization methods include interface engineering, defect engineering, and metal doping to improve the OER performance of TMOs. Among transition metal-based compounds, binary nickel-based materials have been widely developed as highly efficient water splitting electrocatalysts, especially NiMoO4, which is currently the most studied nickel-based electrocatalyst. This is mainly due to the synergistic effect of the excellent water dissociation ability of Ni atoms and the excellent H2 adsorption ability of Mo atoms.

[0004] However, NiMoO4 electrodes are still affected by their poor electronic conductivity, insufficient ion transport and diffusion, and structural instability during long-term cycling. Therefore, the controllable fabrication of NiMoO4 with nanostructures and the rational design of structural engineering are significant and challenging tasks. Specifically, various low-dimensional NiMoO4 nanostructures are directly grown on conductive current collector substrates (e.g., Ni / Cu foam, graphene, and carbon substrates), which reduce charge carrier scattering at grain boundaries and are easily integrated into flexible devices with specific applications, particularly favored for directional electron transport. To overcome the poor conductivity of pure NiMoO4, various NiMoO4 / carbon composites have been synthesized by combining NiMoO4 nanostructures with graphene, carbon nanotubes, conductive polymers, and porous carbon structures. In addition to carbon composites, researchers have also attempted to dope NiMoO4 with several heteroatoms (such as Mn, P, Zn, Ce) or generate oxygen vacancies in the NiMoO4 lattice. Furthermore, NiMoO4 can be composited with other metal oxides or sulfides to form heterostructure electrodes and improve electrochemical performance. However, monotonous strategies sometimes contribute little to the overall improvement of the electrochemical performance of NiMoO4 materials, and some reported composite or doping methods for NiMoO4 involve multiple complex chemical and physical processes, with synthesis routes that are costly or environmentally unfriendly.

[0005] Therefore, finding a low-cost and convenient method to significantly improve the oxygen evolution reaction and hydrogen evolution reaction performance of nickel molybdate materials in transition metal oxides is of research value and application prospect. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a multi-metal oxo acid etching optimized nickel molybdate oxygen evolution electrocatalyst. This method significantly improves the oxygen evolution reaction performance of the binary nickel-based nickel molybdate material, achieving efficient electrocatalytic oxygen evolution reaction while ensuring the stability of the catalytic material.

[0007] The preparation method includes the following steps: flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method are placed in a mixed solution of ethanol, water, and polyoxometalates for etching, washing, and drying to obtain a polyoxometalate-etched nickel molybdate oxygen evolution electrocatalytic material; the polyoxometalates include phosphotungstic acid and phosphomolybdic acid.

[0008] In some embodiments, the sum of the amounts of phosphotungstic acid and phosphomolybdic acid in the 1L mixed solution does not exceed 10 mmol.

[0009] In some embodiments, the volume ratio of ethanol to water is 1:4 to 4:1.

[0010] In some implementations, the etching time is 15 to 90 minutes.

[0011] In some implementations, the washing process specifically involves washing with anhydrous ethanol 3 to 5 times, followed by washing with deionized water 3 to 5 times.

[0012] In some embodiments, the drying temperature is 50–60°C.

[0013] In some embodiments, the preparation method of in-situ synthesis of flower-shaped nickel molybdate nanorods on nickel foam by one-step hydrothermal synthesis is as follows: blocky nickel foam is ultrasonically treated in a mixed solution of hydrochloric acid, ethanol and water for 10 min, washed 2-3 times with ethanol and pure water respectively, and placed in a polytetrafluoroethylene reactor containing a mixed solution of ammonium molybdate tetrahydrate and nickel nitrate hexahydrate. Then, it is reacted at 150°C for 6 hours, cooled to room temperature, washed three times with ethanol and deionized water respectively, and finally dried at 60°C for 10 h to obtain flower-shaped nickel molybdate nanorods.

[0014] In some embodiments, the hydrochloric acid concentration is 12M, and the volume ratio of hydrochloric acid, ethanol, and water is 1:1:1.

[0015] In some embodiments, the concentration of ammonium molybdate tetrahydrate is 15 mM, and the concentration of nickel nitrate hexahydrate is 35 mM.

[0016] In any of the above-described preparation methods, the polyoxometalate etching optimized nickel molybdate oxygen evolution electrocatalyst material can be cut to a suitable size according to actual conditions before use.

[0017] This invention also provides the application of the polyoxometalate etching optimized nickel molybdate oxygen evolution electrocatalyst material obtained by the above preparation method in electrocatalytic water electrolysis.

[0018] Specifically, the above-obtained multi-metal oxoacid etching optimized nickel molybdate oxygen evolution electrocatalyst material was used as the working electrode to assemble a three-electrode test system, with a graphite rod electrode as the counter electrode and Hg / HgO as the reference electrode.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This invention synthesizes nickel molybdate nanorods on nickel foam through a one-step hydrothermal synthesis method. In a mixed solution of ethanol and water, phosphotungstic acid and phosphomolybdic acid etch the nanoflower-like nickel molybdate nanorods grown in situ on nickel foam to obtain an optimized nickel molybdate electrocatalytic material. The charge transfer efficiency is improved, the charge transfer impedance is reduced, and it has good conductivity, which facilitates electron transfer. It also has good chemical stability and structural stability. It can be directly used as a self-supporting electrode for electrocatalytic oxygen evolution reaction. The method is simple, green and environmentally friendly, and has low cost and low production cost.

[0021] (2) In this preparation method, etching nickel molybdate nanorods with polyoxometalates results in a lack of cations (Ni and Mo), changes in the crystal structure, and the formation of a small number of oxygen vacancies while constructing metal defects; etching NMO@NF with polyoxometalates adds n(PO4) to its surface. 3- This adjusts its electronic properties, and the enhanced edge structure has a strong attraction to the -OH groups of the electrolyte, resulting in excellent electrochemical behavior due to structural changes. Metal oxoacid etching improves the valence state of Ni ions in NMO@NF, and the improved valence state of Ni ions is conducive to the formation of NiOOH in the OER process, thus enhancing the catalytic activity of OER.

[0022] (3) The prepared multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalytic material electrode exhibits excellent electrocatalytic oxygen evolution activity and stability. By investigating its electrocatalytic oxygen evolution reaction activity in 1 mol / L KOH electrolyte, the results showed that the current density of PTA&PMA / NMO@NF was 10 mA / cm². 2 The overpotential was only 200 mV, and the Tafel slope was the smallest at 32.8 mV / dec, indicating that the catalyst has good reaction kinetics. After 24 hours of current-time testing, the electrode maintained good stability, and the overpotential remained basically unchanged, demonstrating excellent stability.

[0023] (4) The prepared multi-metal oxo acid etching optimized nickel molybdate oxygen evolution electrocatalyst material not only has excellent electrocatalytic oxygen evolution activity and stability, but also has good electrocatalytic hydrogen evolution activity. Attached Figure Description

[0024] Figure 1 X-ray diffraction patterns of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1.

[0025] Figure 2 Rnman spectra of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1.

[0026] Figure 3 Scanning electron microscope (SEM) images of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1, where (a) is an SEM image of NMO@NF before etching and (b) is an SEM image of PTA&PMA / NMO@NF after etching.

[0027] Figure 4 Transmission electron microscope (TEM) images of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1, where (a) is a TEM image of NMO@NF before etching and (b) is a TEM image of PTA&PMA / NMO@NF after etching.

[0028] Figure 5 High-resolution transmission electron microscope (HRTEM) images of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1, where (a) is an HTEM image of NMO@NF before etching and (b) is an HTEM image of PTA&PMA / NMO@NF after etching.

[0029] Figure 6 EDX mapping of PTA&PMA / NMO@NF prepared in Example 1.

[0030] Figure 7 Ni 2p X-ray high-resolution energy dispersive spectra of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1.

[0031] Figure 8 High-resolution X-ray spectra of Mo 3d prepared in Example 1 for NMO@NF and PTA&PMA / NMO@NF.

[0032] Figure 9 O1s X-ray high-resolution energy spectra of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1.

[0033] Figure 10 Linear scanning curves of the oxygen evolution reaction in 1M KOH electrolyte using NMO@NF and PTA&PMA / NMO@NF prepared in Example 1 as electrocatalysts.

[0034] Figure 11 Tafel curves of the oxygen evolution reaction of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1 as electrocatalysts in 1M KOH electrolyte.

[0035] Figure 12 Example 1: AC impedance curves of the oxygen evolution reaction in 1M KOH electrolyte using NMO@NF and PTA&PMA / NMO@NF as electrocatalysts.

[0036] Figure 13 Example 1: 24-hour stability diagram of the oxygen evolution reaction current-time of NMO@NF and PTA&PMA / NMO@NF as electrocatalysts in 1M KOH electrolyte.

[0037] Figure 14 Linear scanning curves of the hydrogen evolution reaction in 1M KOH electrolyte using NMO@NF and PTA&PMA / NMO@NF prepared in Example 1 as electrocatalysts.

[0038] Figure 15Tafel curves of the hydrogen evolution reaction of NMO@NF and PTA&PMA / NMO@NF prepared in Example 1 as electrocatalysts in 1M KOH electrolyte.

[0039] Figure 16 Example 1: AC impedance curves of the hydrogen evolution reaction of NMO@NF and PTA&PMA / NMO@NF as electrocatalysts in 1M KOH electrolyte. Detailed Implementation

[0040] The following examples further illustrate specific implementations of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to existing technology.

[0041] Example 1

[0042] (1) Flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam using a one-step hydrothermal synthesis method: Commercially available bulk nickel foam (NF) was cut into small pieces (1.0 cm * 1.5 cm) and ultrasonically treated for 10 min in a mixed solution of hydrochloric acid (12.0 mol / L), ethanol, and water (volume ratio 1:1:1). After removal, the nanorods were washed three times with ethanol and pure water, respectively, and the surface moisture was absorbed with filter paper. 139 mg of ammonium molybdate tetrahydrate and 76 mg of nickel nitrate hexahydrate were ultrasonically dissolved in 7.5 mL of deionized water for 30 min and then added to a polytetrafluoroethylene reactor (25.0 mL). A piece of pretreated nickel foam was then placed in the reactor and heated in a drying oven at 150 °C for 6 h. After cooling to room temperature, the nanorods were washed three times with ethanol and deionized water, respectively, and finally dried at 60 °C for 10 h to obtain flower-shaped nickel molybdate nanorods (NMO@NF).

[0043] (2) Prepare a 10 mL mixture of ethanol and deionized water containing 115.2 mg phosphotungstic acid (PTA) and 18.3 mg phosphomolybdic acid (PMA) (ethanol:water = 2:1). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 15 min. After etching, remove the nanorods and wash them three times with ethanol and deionized water respectively. Dry them in an oven at 60 °C to obtain the multi-metal oxoacid etching optimized nickel molybdate oxygen evolution electrocatalyst material (PTA&PMA / NMO@NF).

[0044] X-ray diffraction was performed on NMO@NF and PTA&PMA / NMO@NF before and after etching. Comparison with standard spectra showed that NMO@NF was successfully synthesized. Figure 1 It can be seen that the lattice constant and volume increase slightly after etching.

[0045] The NMO@NF and PTA&PMA / NMO@NF samples before and after etching were characterized using Rnman spectroscopy. Figure 2 It can be seen that the Raman spectrum shifts to higher frequencies, indicating the generation of cation defects and changes in the crystal lattice after etching.

[0046] Electron microscopy was used to scan NMO@NF and PTA&PMA / NMO@NF before and after etching. Figure 3 It can be seen that before etching, NF was almost completely covered by flower-like clusters composed of NMO nanorods, and the overall morphology did not change significantly after etching.

[0047] The NMO@NF and PTA&PMA / NMO@NF samples before and after etching were scanned using a transmission electron microscope. Figure 4 This demonstrates that after etching, metal precipitates out, and the surface area becomes loose and develops defects.

[0048] The NMO@NF and PTA&PMA / NMO@NF samples before and after etching were scanned using a high-resolution transmission electron microscope. Figure 5 This indicates that some lattice distortion exists at the interface due to the precipitation of two cations (nickel and molybdenum) during the etching process.

[0049] Map PTA & PMA / NMO@NF using EDX. Figure 6 This indicates that Ni, Mo, O, P, and W are uniformly distributed.

[0050] NMO@NF and PTA&PMA / NMO@NF before and after etching were irradiated with X-rays. Figure 7 Ni 2p、 Figure 8 Mo 3d and Figure 9 The high-resolution energy dispersive spectroscopy (EDS) of O 1s confirmed the presence of Ni, Mo, and O atoms, and also confirmed the change in the valence state of Ni atoms before and after nickel molybdate etching. 3+ The proportion of ions increased significantly.

[0051] Example 2

[0052] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0053] Prepare a 10 mL mixture of ethanol and deionized water (ethanol:water = 1:1) containing 115.2 mg phosphotungstic acid (PTA) and 18.3 mg phosphomolybdic acid (PMA). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 15 min. After etching, remove the nanorods, wash them three times with ethanol, then wash them four times with deionized water, and dry them in an oven at 50 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0054] Example 3

[0055] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0056] Prepare a 10 mL mixture of ethanol and deionized water (ethanol:water = 3:1) containing 72 mg phosphotungstic acid (PTA) and 45.6 mg phosphomolybdic acid (PMA). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 90 min. After etching, remove the nanorods and wash them five times with ethanol and five times with deionized water, respectively. Dry them in an oven at 55 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0057] Example 4

[0058] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0059] Prepare a 10 mL mixture of ethanol and deionized water (ethanol:water = 4:1) containing 115.2 mg phosphotungstic acid (PTA) and 18.3 mg phosphomolybdic acid (PMA). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 60 min. After etching, remove the nanorods and wash them four times with ethanol and deionized water respectively. Dry them in an oven at 60 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0060] Example 5

[0061] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0062] A 10 mL mixture of ethanol and deionized water (ethanol:water = 1:4) containing 28.8 mg phosphotungstic acid (PTA) and 73.2 mg phosphomolybdic acid (PMA) was prepared. Then, flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method were placed in the mixture and etched for 80 min. After etching, the nanorods were removed, washed four times with ethanol, then washed three times with deionized water, and dried in an oven at 55 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0063] Example 6

[0064] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0065] Prepare a 10 mL mixture of ethanol and deionized water (ethanol:water = 1:2) containing 2.88 mg phosphotungstic acid (PTA) and 164.25 mg phosphomolybdic acid (PMA). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 70 min. After etching, remove the nanorods, wash them three times with ethanol, then wash them five times with deionized water, and dry them in an oven at 55 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0066] Example 7

[0067] Step (1) of this embodiment is the same as that of embodiment 1, and step (2) is as follows:

[0068] Prepare a 10 mL mixture of ethanol and deionized water (ethanol:water = 1:3) containing 2.88 mg phosphotungstic acid (PTA) and 1.64 mg phosphomolybdic acid (PMA). Then, place the flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method into the mixture and etch for 30 min. After etching, remove the nanorods, wash them three times with ethanol, then wash them three times with deionized water, and dry them in an oven at 55 °C to obtain a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst material.

[0069] Experiment Example 1: Electrochemical Performance Testing

[0070] 1. Testing method:

[0071] All electrochemical data were acquired using a CHI 660E electrochemical workstation equipped with a three-electrode system.

[0072] The prepared catalyst was loaded onto NF as the working electrode, with a Hg / HgO electrode and a graphite electrode serving as the reference and counter electrodes, respectively. The working electrode had a geometric area of ​​1.0 cm × 1.0 cm immersed in the electrolyte. All potentials measured at the Hg / HgO electrode were calibrated to the potentials at the reversible hydrogen electrode (RHE). Oxygen evolution reaction (OER) experiments were conducted in 1 M KOH solution using linear sweep voltammetry (LSV) at a scan rate of 5 mV / s within a voltage range of 0–1.0 V.

[0073] The Tafel slope of the sample was linearly fitted according to the Tafel equation (η = b log j + a, where η is the overpotential, b is the Tafel slope, and j is the current density).

[0074] Electrochemical impedance spectroscopy (EIS) was used to determine the electrolyte resistance R of different catalysts in the range of 10 kHz to 0.01 Hz. s and charge transfer resistance R ct Its 24-hour stability was measured using the chronoamperometry method.

[0075] The NMO@NF prepared in Example 1 and the etch-optimized PTA & PMA / NMO@NF were cut into 1cm × 1cm sizes and used as working electrodes for testing.

[0076] 2. Test Results:

[0077] Figure 10-13 The graph shows the electrocatalytic oxygen evolution data of NiMoO4@NF prepared in Example 1 before and after etching treatment, as an electrocatalyst in 1M KOH electrolyte.

[0078] Figure 10 and Figure 11 The results show that the overpotential of PTA&PMA / NMO@NF is significantly reduced, achieving 10 mA / cm² at only 200 mV. 2 The current density was reduced to 100 mA / cm² at only 230 mV. 2 The current density of NMO@NF requires an overpotential of 227 mV to achieve 10 mA / cm². 2 The current density can only be achieved at an overpotential of 267mV to reach 100mA / cm. 2 The current density was [not specified]. Furthermore, the Tafel slope of PTA&PMA / NMO@NF was 29.4 mV / dec, significantly lower than that of NMO@NF (44.2 mV / dec), indicating that PTA&PMA / NMO@NF exhibits good reaction kinetics and is more conducive to catalytic reactions.

[0079] Depend on Figure 12 The charge transfer resistance (R) of PTA & PMA / NMO@NF ct The charge transfer resistance (CTR) is 1.5Ω, significantly lower than that of NMO@NF (3.7Ω). Therefore, the PTA&PMA / NMO@NF electrode exhibits better conductivity and a faster electron transfer rate.

[0080] Depend on Figure 13 After a 24-hour time-current stability test, the curve remained basically stable, and the overpotential remained essentially unchanged, demonstrating that PTA&PMA / NMO@NF exhibits outstanding electrochemical stability in the electrochemical process of the oxygen evolution reaction.

[0081] Figure 14-16 The graph shows the electrocatalytic hydrogen evolution data of NiMoO4@NF prepared in Example 1 before and after etching treatment, as an electrocatalyst in 1M KOH electrolyte.

[0082] Figure 14 The display shows that NMO / NF is at 10 mA / cm 2The highest overpotential of 167 mV was observed at this location, and the PTA&PMA / NMO@NF obtained after etching exhibited an overpotential of 10 mA / cm. 2 The overpotential was 119mV, which is significantly lower than that of NMO / NF, indicating that the etching modification significantly improves the hydrogen evolution reaction activity.

[0083] Figure 15 The results show that the Tafel slope of PTA&PMA / NMO@NF is 113.2 mV / dec, which is lower than the slope of NMO@NF (180.0 mV / dec). This indicates that PTA&PMA / NMO@NF has better hydrogen evolution reaction kinetics than NMO@NF, and the etch-modified catalysts of phosphotungstic acid and phosphomolybdic acid are very favorable for the HER reaction.

[0084] Figure 16 The charge transfer resistance (R) of PTA&PMA / NMO@NF is shown. ct The charge transfer resistance (CTR) is 3.7 Ω, which is significantly lower than that of NMO@NF (6.4 Ω), indicating that the PTA&PMA / NMO@NF electrode also has better conductivity and faster reaction kinetics in the hydrogen evolution reaction.

[0085] Table 1 compares the OER performance of PTA&PMA / NMO@NF with other electrocatalysts using 1M KOH as the electrolyte. The lowest overpotential of PTA&PMA / NMO@NF is 200mV, and the Tafel slope is 32.8mV / dec. It can be seen that the OER activity of PTA&PMA / NMO@NF is better than most previously reported transition metal catalysts.

[0086] Table 1

[0087]

[0088] (1)Jiang, R.; Zhao, D.; Fan, H.;

[0089] (2)Xie,W.;Huang,J.;Huang,L.;Geng,S.;Song,S.;Tsiakaras,P.;Wang,Y.,Novelfluorine-doped cobalt molybdate nanosheets with enriched oxygen-vacancies for improved oxygenevolution reaction activity.Applied Catalysis B:Environmental 2022,303,120871.

[0090] (3)Jiang,T.;Xie,W.;Geng,S.;Li,R.;Song,S.;Wang,Y.,Constructingoxygenvacancy-regulated cobalt molybdate nanoflakes for efficient oxygenevolution reaction catalysis.Chinese Journal of Catalysis 2022,43(9),2434-2442.

[0091] (4)Zhu,J.;Qian,J.;Peng,X.;Xia,B.;Gao,D.,Etching-induced surfacereconstruction ofNiMoO4 for oxygen evolution reaction.Nano-micro letters2023,15(1),30.

[0092] (5)Cai,Z.;Wang,P.;Zhang,J.;Chen,A.;Zhang,J.;Yan,Y.;Wang,X.,Reinforcedlayereddouble hydroxide oxygen-evolution electrocatalysts:a polyoxometallicacid wet-etching approachand synergistic mechanism.Advanced Materials 2022,34(26),2110696.

[0093] (6) Dalai, N.; Jena, B., Iron nickel sulfide nanorods for oxygen and hydrogen evolution reaction. ChemistrySelect 2023, 8(13), e202204370.

[0094] (7)Choi, S.; Kim, S.-J.; Han, S.; Wang, J.; Kim, J.; Koo, B.; Ryabin, AA; Kunze, S.; Hyun, H.; Han, J., Enhancing Oxygen Evolution Reaction via a SurfaceReconstruction-Induced LatticeOxygen Mechanism.ACS Catalysis 2024,14(20),15096-15107.

[0095] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a multi-metal oxoacid etching-optimized nickel molybdate oxygen evolution electrocatalyst, characterized in that, The preparation method includes the following steps: flower-shaped nickel molybdate nanorods synthesized in situ on nickel foam by a one-step hydrothermal synthesis method are placed in a mixed solution of ethanol, water, and polyoxometalates for etching, washing, and drying to obtain a polyoxometalate-etched nickel molybdate oxygen evolution electrocatalytic material; the polyoxometalates include phosphotungstic acid and phosphomolybdic acid; the sum of the amounts of phosphotungstic acid and phosphomolybdic acid in 1L of the mixed solution does not exceed 10 mmol; the volume ratio of ethanol to water is 1:4 to 4:1; the etching time is 15 to 90 min.

2. The preparation method according to claim 1, characterized in that, The washing process specifically involves washing with anhydrous ethanol 3-5 times, followed by washing with deionized water 3-5 times.

3. The preparation method according to claim 1, characterized in that, The drying temperature is 50~60℃.

4. The preparation method according to claim 1, characterized in that, The preparation method of in-situ synthesis of flower-shaped nickel molybdate nanorods on nickel foam by the one-step hydrothermal synthesis method is as follows: blocky nickel foam is ultrasonically treated in a mixed solution of hydrochloric acid, ethanol and water for 10 min, washed 2-3 times with ethanol and pure water respectively, and placed in a polytetrafluoroethylene reactor containing a mixed solution of ammonium molybdate tetrahydrate and nickel nitrate hexahydrate. Then, it is reacted at 150℃ for 6 h, cooled to room temperature, washed three times with ethanol and deionized water respectively, and finally dried at 60℃ for 10 h to obtain flower-shaped nickel molybdate nanorods.

5. The preparation method according to claim 4, characterized in that, The hydrochloric acid concentration is 12M, and the volume ratio of hydrochloric acid, ethanol, and water is 1:1:

1.

6. The preparation method according to claim 4, characterized in that, The concentration of ammonium molybdate tetrahydrate is 15 mM, and the concentration of nickel nitrate hexahydrate is 35 mM.

7. The application of the polyoxometalate etching optimized nickel molybdate oxygen evolution electrocatalyst material prepared by the preparation method according to any one of claims 1-6 in electrocatalytic water electrolysis.

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