Transition metal doped nickel oxide-based catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oxygen evolution catalysts, and particularly relates to a transition metal doped nickel oxide-based catalyst as well as a preparation method and application thereof. The method comprises the following steps: loading nickel oxide on a conductive substrate to form a working electrode, carrying out pulse activation on the nickel oxide by taking potassium hydroxide as a first electrolyte and adopting a pulse potentiometric method, and inducing formation of oxygen vacancies and lattice distortion on the surface of the nickel oxide to obtain a nickel oxide matrix; and with the nickel oxide substrate as a working electrode, a transition metal salt solution as a second electrolyte and transition metal salts as soluble divalent cobalt salt and soluble trivalent iron salt, performing electrochemical in-situ deposition under a constant voltage to obtain the transition metal doped nickel oxide-based catalyst. Through a strategy of combining electrochemical activation and transition metal co-deposition, controllable construction of surface defect engineering and a heterogeneous interface is realized, and the cobalt-iron co-doped nickel oxide-based material with high activity, high stability and self-reconfiguration characteristics is provided, so that the catalytic performance of an oxygen evolution reaction and the long-term operation stability are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of oxygen evolution catalysts, and in particular relates to a transition metal-doped nickel oxide-based catalyst and a preparation method and application thereof. Background Art

[0002] Hydrogen energy, due to its high energy density and environmentally friendly properties, is considered an ideal alternative to fossil fuels. Electrochemical water splitting technology produces green hydrogen through the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). The OER, involving a four-electron transfer process, has slow kinetics and a high overpotential, necessitating the use of efficient catalysts.

[0003] Nickel-based oxides such as NiO, NiFeO x 、NiCoO x Due to its adjustable electronic structure and diverse redox properties, it has become a candidate material for alkaline OER catalysts. However, existing nickel-based oxide catalysts such as NiO, NiFeO X In alkaline OER, firstly, due to the strong covalency of the Ni-O bond, the adsorption energy barrier of oxygen intermediates such as *OH, *O, and *OOH is high, resulting in insufficient intrinsic catalytic activity. Usually, an overpotential of more than 300 mV is required to reach 10 mA / cm 2 The current density is much higher than the 285mV of precious metal-based catalysts such as RuO2. Secondly, traditional nickel-based oxides are prone to uncontrollable surface reconstruction during electrochemical activation, such as lattice reorganization, phase transition, and anion insertion, generating metastable NiOOH or Ni(OH)2 phases with low active site density and poor stability. After long-term operation, they are prone to performance degradation due to structural collapse or active phase deactivation, such as complete deactivation after 50 hours.

[0004] The strong covalency of the Ni-O bond results in poor adsorption energy for oxygen intermediates, limiting their intrinsic activity. Existing technologies optimize nickel-based oxides through strategies such as doping, often relying on precious metal doping such as Ru and Ir to enhance activity. However, high costs and resource scarcity severely restrict their large-scale application. However, the following problems still exist: the surface reconstruction process is uncontrollable, and metastable phases are easily generated, resulting in insufficient exposure of active sites and high charge transfer resistance; the lack of systematic regulation of interfacial reconstruction behavior makes it difficult to balance activity and durability, limiting the practical application potential of nickel-based catalysts. Summary of the Invention

[0005] To address these issues, the present invention provides a transition-metal-doped nickel oxide-based catalyst, its preparation method, and its application. By combining electrochemical activation with transition-metal co-deposition, surface defect engineering and controllable heterogeneous interface construction are achieved, resulting in a cobalt-iron co-doped nickel oxide-based material with high activity, high stability, and self-reconstruction properties, significantly improving the catalytic performance and long-term operational stability of the oxygen evolution reaction.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The first object of the present invention is to provide a method for preparing a transition metal-doped nickel oxide-based catalyst, comprising the following steps: S1. Nickel oxide is loaded on a conductive substrate to form a working electrode. Potassium hydroxide is used as the first electrolyte. The nickel oxide is pulse activated by a pulse potential method to induce the formation of oxygen vacancies and lattice distortion on the surface of the nickel oxide to obtain a nickel oxide matrix.

[0008] S2. Using nickel oxide substrate as the working electrode and transition metal salt solution as the second electrolyte, the transition metal salts are soluble divalent cobalt salt and soluble trivalent iron salt, and electrochemical in-situ deposition is performed under a constant voltage to obtain a transition metal-doped nickel oxide-based catalyst.

[0009] It should be noted that the present invention uses nickel oxide loaded on a conductive substrate. A pulsed potential is used to induce oxygen vacancies and lattice distortion on the nickel oxide surface, forming a composite shell on the nickel oxide surface. The composite shell is composed of amorphous Ni(OH)2 and NiOOH, which increases the density of active sites. The nickel oxide substrate is then doped with transition metal elements Co and Fe on the composite shell by electrochemical in situ deposition. The Co, Fe, and composite shell form a heterogeneous synergistic catalytic interface. Since the transition metal elements are reduced to a low oxidation state during the electrochemical in situ deposition process, the low oxidation state transition metal elements are further polarized by the anodic potential during the OER process, driving a large-scale rearrangement of the chemical bonds on their surface to minimize the total free energy of the catalytic system. The resulting dynamically stable Ni-O-Co / Fe active sites have significantly enhanced corrosion resistance, and the overpotential remains stable during testing for up to 900 hours, showing potential for industrial application.

[0010] In some embodiments, the pulse potential method adopts a three-electrode system, the counter electrode is a graphite electrode, the reference electrode is Hg / HgO or Ag / AgCl, the potential of the working electrode is -0.5V vs.RHE to -2V vs.RHE, the potential of the counter electrode is 2Vvs.RHE to 4V vs.RHE, the pulse width is 0.1s to 1s, and the pulse cycle parameters are 50 times to 300 times; the concentration of potassium hydroxide is 0.05M to 1M.

[0011] It should be noted that the present invention adopts a pulse activation method. Under alternating anode and cathode potentials, the hydroxide ions in the electrolyte collide with the NiO in different ways. x The surface of the anode potential. - The kinetic energy of NiO increases, and the physical impact causes the surface atoms to rearrange, stripping the passivation layer and exposing fresh active sites. 2+ Further oxidized to high-valent Ni 3+ Or NiOOH, forming oxygen-rich vacancies or lattice distortion. Under cathode potential: cathode electric field attracts OH - Directed migration to the surface, partially embedded in the lattice gap or adsorbed in oxygen vacancies, repairing local defects while regulating the electronic structure, high-priced Ni 3+ Species are reduced to Ni 2+ , accompanied by proton embedding into the crystal lattice. This periodic oxidation-reduction cycle breaks the thermodynamic equilibrium, promotes the formation of amorphous / grain boundary phase, increases the specific surface area and active site density. In addition, the high electric field at the anodic stage accelerates OH - The cathodic phase promotes ion insertion, and the two alternately suppress the passivation or dissolution caused by a single polarization.

[0012] In some embodiments, the loading amount of nickel oxide on the conductive substrate is 0.5 mg / cm 2 ~2mg / cm 2 , the conductive substrate is carbon paper, carbon cloth or nickel foam.

[0013] It should be noted that during the OER reaction, only the surface of the catalyst occurs. The rest of the anode acts as an electron collector, requiring excellent conductivity. Therefore, the nickel oxide needs to be loaded on a conductive substrate. The specific method of loading the nickel oxide on the conductive substrate is to mix the nickel oxide and perfluorosulfonic acid polymer at a mass volume ratio of 1mg:10μL, disperse them in an alcohol solvent, which can be ethanol or isopropanol, and evenly apply them to the conductive substrate. The resulting nickel oxide / conductive substrate is dried.

[0014] In some embodiments, the total concentration of transition metal ions in the transition metal salt solution is 0.1M to 0.3M, and the molar ratio of cobalt to iron in the soluble divalent cobalt salt and the soluble ferric iron salt is 1:0.2-2.

[0015] It should be noted that the present invention loads Co and Fe on the composite shell in a co-doped manner. Co, Fe and the composite shell form a heterogeneous interface, stabilize the Ni-O-Co / Fe active sites, and inhibit structural collapse, thereby significantly improving the OER catalytic performance and long-term operation stability. The present invention is not limited to the specific types of soluble divalent cobalt salts and soluble trivalent iron salts. As long as they are easily soluble in water, the soluble divalent cobalt salts or soluble trivalent iron salts can be nitrates, sulfates or chlorides, etc.

[0016] In some embodiments, the constant voltage potential is -0.5 V vs. SCE to -2 V vs. SCE, the deposition temperature is room temperature, and the deposition time is 10 min to 80 min.

[0017] It should be noted that in nickel oxide NiO x When electrodepositing transition metal elements on a surface, parameters such as voltage and deposition time significantly influence the chemical composition, microstructure, and interfacial properties of the deposited layer. The voltage determines the deposition rate of the metal ions. Excessively high cathode voltage accelerates metal ion deposition, resulting in an uneven and rough deposit. Conversely, a low voltage results in a uniform and smooth deposit. Deposition time also affects the thickness of the deposited layer. Therefore, voltage and deposition time must be controlled to achieve a deposit with the appropriate roughness and thickness.

[0018] In some embodiments, the method for preparing nickel oxide comprises the following steps: The soluble nickel salt and the complexing agent are dissolved in a solvent, complexed to form a complex, and then an alcohol inducer is added to induce the complex to precipitate, thereby obtaining the nickel complex.

[0019] The nickel complex is calcined at 400° C. to 600° C. to obtain nickel oxide.

[0020] In some embodiments, the molar ratio of the soluble nickel salt to the complexing agent is 1:1-3, the complexing agent is α-alanine, the volume ratio of the alcohol inducer to the solvent is 10-15:1, and the alcohol inducer is ethanol, isopropanol or methanol; the calcination heating rate is 1°C / min-5°C / min, and the calcination holding time is 1h-6h.

[0021] It is important to note that the stereostructure and coordination of α-alanine guide the growth of specific crystal planes. The polarity of water promotes complex ionization, while the weak polarity of alcohol restricts diffusion, forming localized supersaturated regions and achieving a kinetic equilibrium of "slow reaction, fast assembly." During calcination, the precursor (such as the Ni-alanine complex) gradually removes organic matter. Slow heating prevents structural collapse caused by drastic decomposition and reduces lattice distortion and microcracks. Extending the holding time promotes the complete oxidation of the Ni-amino acid complex, forming NiO with excellent crystallinity, ensuring structural stability during the OER process.

[0022] It should be noted that the solvent is deionized water, and the amount of alcohol inducer used is only related to the amount of deionized water used. The alcohol inducer is used to regulate the overall polarity of the deionized water, causing local supersaturation and promoting the precipitation of the nickel complex.

[0023] The present invention also provides a transition metal-doped nickel oxide-based catalyst prepared using the above-mentioned preparation method. The transition metal-doped nickel oxide-based catalyst uses a conductive substrate as a carrier, the carrier supporting a nickel oxide matrix, the surface of the nickel oxide matrix supporting a composite shell layer, the composite shell layer being composed of amorphous Ni(OH)2 / NiOOH, the surface of the composite shell layer being doped with a transition metal element, the doping amount of the transition metal element being 1% to 10% of the atomic ratio of the composite shell layer surface, the nickel oxide matrix having a cubic phase, the particle size of the nickel oxide matrix ranging from 20 nm to 100 nm, and the thickness of the composite shell layer being 1 nm to 10 nm.

[0024] In addition, the present invention also provides the use of the above transition metal-doped nickel oxide-based catalyst in electrocatalytic water decomposition.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (4) The preparation method of the transition metal-doped nickel oxide-based catalyst provided by the present invention is to load nickel oxide on a conductive substrate, induce oxygen vacancies and lattice distortion on the surface of nickel oxide by pulse potential, and form a composite shell on the surface of nickel oxide. The composite shell is composed of amorphous Ni(OH)2 and NiOOH, which increases the density of active sites. Then, the transition metal elements Co and Fe are doped on the composite shell by electrochemical in situ deposition on the nickel oxide substrate, and Co, Fe and the composite shell form a heterogeneous synergistic catalytic interface. Since the transition metal elements are reduced to a low oxidation state during the electrochemical in situ deposition process, the low oxidation state transition metal elements are further polarized by the anodic potential during the OER process, thereby driving the chemical bonds on their surface to undergo large-scale rearrangement to minimize the total free energy of the catalytic system. The dynamically stable Ni-O-Co / Fe active sites formed have significantly enhanced corrosion resistance, and the overpotential remains stable during the test process of up to 900 hours, which has the potential for industrial application.

[0026] (5) The pulse activation method adopted by the present invention is that under alternating anode and cathode potentials, the hydroxide ions in the electrolyte collide with NiO in different ways. x The surface of the anode potential. - The kinetic energy of NiO increases, and the physical impact causes the surface atoms to rearrange, stripping the passivation layer and exposing fresh active sites. 2+ Further oxidized to high-valent Ni 3+ Or NiOOH, forming oxygen-rich vacancies or lattice distortion. Under cathode potential: cathode electric field attracts OH - Directed migration to the surface, partially embedded in the lattice gap or adsorbed in oxygen vacancies, repairing local defects while regulating the electronic structure, high-priced Ni 3+ Species are reduced to Ni 2+, accompanied by proton embedding into the crystal lattice. This periodic oxidation-reduction cycle breaks the thermodynamic equilibrium, promotes the formation of amorphous / grain boundary phases, and increases the specific surface area and active site density. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 NiO was prepared in Comparative Example 5 of the present invention. x Particles and pNiO prepared in Comparative Example 6 x X-ray diffraction patterns of the catalyst.

[0028] Figure 2 pNiO prepared in Comparative Example 6 of the present invention x The morphology of the catalyst, Figure 2 Figure a is a scanning electron microscope image, Figure b is a transmission electron microscope image, and Figure c is a high-angle annular dark-field scanning transmission electron microscope image.

[0029] Figure 3 Co2Fe1-pNiO prepared in Example 1 of the present invention x Catalyst, Co1Fe2-pNiO prepared in Example 2 x Catalyst, Comparative Example 3 Preparation of Fe-pNiO x Catalyst and Comparative Example 4 Preparation of Co-pNiO x Scanning electron micrograph of the catalyst. Figure 3 Figure a1 shows the Co2Fe1-pNiO prepared in Example 1 at a size of 200 nm. x Catalyst, Figure a2 shows the Co2Fe1-pNiO prepared in Example 1 at 1 μm size x Catalyst, Figure b1 shows the Co1Fe2-pNiO prepared in Example 2 at a size of 200 nm x Catalyst, Figure b2 shows Co1Fe2-pNiO prepared in Example 2 at 1 μm size x Catalyst, Figure c1 shows Fe-pNiO prepared in Comparative Example 3 at 200nm size x Catalyst, Figure c2 shows Fe-pNiO prepared in Comparative Example 3 at 1 μm size x Catalyst, d1 shows Co-pNiO prepared in comparative example 4 at 200nm size x Catalyst, d2 is the Co-pNiO prepared in comparative example 4 at 1 μm size x catalyst.

[0030] Figure 4 Preparation of pNiO for Comparative Example 1 of the present invention x Catalyst, Comparative Example 5 Preparation of NiO x Catalyst, Comparative Example 6 Preparation of oNiO x Catalyst and Comparative Example 7 Preparation of rNiO xX-ray photoelectron spectroscopy of the catalyst, Figure 4 Figure a in the figure is Ni 2p 3 / 2 Spectrum, Figure b is the O 1s spectrum.

[0031] Figure 5 NiO was prepared in Comparative Example 5 of the present invention. x Catalyst and Comparative Example 6 Preparation of pNiO x Raman spectra of the catalyst and its comparative example.

[0032] Figure 6 Co2Fe1-pNiO prepared in Example 1 of the present invention x Catalyst, Comparative Example 3 Preparation of Fe-pNiO x Catalyst, Comparative Example 4 Preparation of Co-pNiO x Catalyst and Comparative Example 6 Preparation of pNiO x X-ray photoelectron spectroscopy of the catalyst, Figure 6 Figure a is the O1s spectrum, and Figure b is the Ni 2p spectrum. 3 / 2 Spectrum, Figure c is Co2Fe1-pNiO x Catalyst and Fe-pNiO x Fe 2p spectrum of the catalyst, d is Co2Fe1-pNiO x Catalyst and Co-pNiO x Co 2p spectrum of the catalyst.

[0033] Figure 7 The LSV curves of the catalysts prepared in Example 1 and Examples 3 to 5 are shown.

[0034] Figure 8 This is an LSV curve diagram of the catalysts prepared in Examples 1 to 2 and Comparative Examples 1 to 8 of the present invention.

[0035] Figure 9 The stability test curves of the catalysts of Example 1, Comparative Example 6 and Comparative Example 8 of the present invention are shown. DETAILED DESCRIPTION

[0036] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present 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.

[0038] The following is further described through specific examples.

[0039] Example 1 A method for preparing a transition metal-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0040] The nickel-alanine complex was placed in a muffle furnace and heated to 600°C at a rate of 1°C / min. It was calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0041] S2, 1mg of NiO x The particles were mixed with 200 μL of ethanol and 10 μL of perfluorosulfonic acid polymer, and then ultrasonically dispersed. The mixture was coated on a 1 cm × 1 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0042] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite as the counter electrode, and Hg / HgO as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 100 times to obtain a nickel oxide matrix.

[0043] S4. Prepare the electrolyte: Mix a 0.1M Co(NO3)2 aqueous solution and a 0.05M Fe(NO3)3 aqueous solution to form an electrolyte. The total concentration of transition metal ions in the electrolyte is 0.15M. Use a three-electrode system with nickel oxide substrate as the working electrode, graphite as the counter electrode, and saturated calomel electrode as the reference electrode. Electrochemical in situ deposition at -1V vs. SCE for 20min is performed to obtain a transition metal-doped nickel oxide-based catalyst, named Co2Fe1-pNiO x .

[0044] Example 2 A method for preparing a transition metal-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0045] The nickel-alanine complex was placed in a muffle furnace and heated to 600°C at a rate of 1°C / min. It was calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0046] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0047] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite was used as the counter electrode, and Hg / HgO was used as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate the nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0048] S4. Prepare the electrolyte: Mix a 0.1M Co(NO3)2 aqueous solution and a 0.05M Fe(NO3)3 aqueous solution to form an electrolyte with a total transition metal ion concentration of 0.15M. Use a three-electrode system with nickel oxide substrate as the working electrode, graphite as the counter electrode, and Hg / HgO as the reference electrode. Electrochemical in situ deposition at -1V vs. SCE for 20min is performed to obtain a transition metal-doped nickel oxide-based catalyst, named Co1Fe2-pNiO. x -20.

[0049] Example 3 A method for preparing a transition metal-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0050] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0051] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0052] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite as the counter electrode, and Hg / HgO as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0053] S4. Prepare the electrolyte: Mix a 0.1M Co(NO3)2 aqueous solution and a 0.05M Fe(NO3)3 aqueous solution to form an electrolyte with a total transition metal ion concentration of 0.15M. Use a three-electrode system with nickel oxide substrate as the working electrode, graphite as the counter electrode, and Hg / HgO as the reference electrode. Electrochemical in situ deposition at -1V vs. SCE for 10min is performed to obtain a transition metal-doped nickel oxide-based catalyst named Co2Fe1-pNiO. x -10.

[0054] Example 4 A method for preparing a transition metal-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0055] The nickel-alanine complex was placed in a muffle furnace and heated to 600°C at a rate of 1°C / min. It was calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0056] S2, 0.25mg NiO x The particles, 50 μL of ethanol, and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0057] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite was used as the counter electrode, and Hg / HgO was used as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate the nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0058] S4. Prepare the electrolyte: Mix a 0.1M Co(NO3)2 aqueous solution and a 0.05M Fe(NO3)3 aqueous solution to form an electrolyte. The total concentration of transition metal ions in the electrolyte is 0.15M. Use a three-electrode system with nickel oxide substrate as the working electrode, graphite as the counter electrode, and Hg / HgO as the reference electrode. Electrochemical in situ deposition at -1V vs. SCE for 40min is performed to obtain a transition metal-doped nickel oxide-based catalyst, named Co2Fe1-pNiO. x -40.

[0059] Example 5 A method for preparing a transition metal-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0060] The nickel-alanine complex was placed in a muffle furnace and heated to 600°C at a rate of 1°C / min. It was calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0061] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0062] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite was used as the counter electrode, and Hg / HgO was used as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate the nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0063] S4. Prepare the electrolyte: Mix a 0.1M Co(NO3)2 aqueous solution and a 0.05M Fe(NO3)3 aqueous solution to form an electrolyte. The total concentration of transition metal ions in the electrolyte is 0.15M. Use a three-electrode system with a nickel oxide substrate as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Electrochemical in situ deposition at -1V vs. SCE for 80min is performed to obtain a transition metal-doped nickel oxide-based catalyst, named Co2Fe1-pNiO. x -80.

[0064] Comparative Example 1 A method for preparing a defective nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0065] The nickel-alanine complex was placed in a muffle furnace and heated to 600°C at a rate of 1°C / min. It was calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0066] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0067] S3, using a three-electrode system with NiO x / carbon paper as the working electrode, graphite as the counter electrode and Hg / HgO as the reference electrode, with a 1M potassium hydroxide solution as the electrolyte, a pulse potential was applied to the nickel oxide for pulse activation, wherein the pulse width was 1s, the cathode potential was -1V vs.RHE → the anode potential was 3V vs.RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix; that is, a defective nickel oxide-based catalyst, named pNiO x catalyst.

[0068] Comparative Example 2 A method for preparing a Mn-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0069] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0070] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0071] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, carbon rod as the counter electrode, and Hg / HgO as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0072] S4. Prepare the electrolyte: A 0.15M Mn(NO3)2 aqueous solution was used as the electrolyte. A three-electrode system was used with nickel oxide substrate as the working electrode, graphite as the counter electrode, and saturated calomel electrode as the reference electrode. Constant potential electrochemical in situ deposition was performed at -1V vs. SCE for 20min to obtain a Mn-doped nickel oxide-based catalyst named Mn-pNiO. x catalyst.

[0073] Comparative Example 3 A method for preparing an Fe-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0074] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0075] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0076] S3, using a three-electrode system with NiO x / carbon paper as the working electrode, graphite as the counter electrode and Hg / HgO as the reference electrode, with a 1 M potassium hydroxide solution as the electrolyte, a pulse potential was applied to the nickel oxide for pulse activation, wherein the pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix; S4. Prepare the electrolyte: A 0.15M Fe(NO3)2 aqueous solution was used as the electrolyte. A three-electrode system was used, with nickel oxide substrate as the working electrode, graphite as the counter electrode, and saturated calomel electrode as the reference electrode. Constant potential electrochemical in situ deposition was performed at -1V vs. SCE for 20min to obtain Fe-doped nickel oxide-based catalyst, named Fe-pNiO x catalyst.

[0077] Comparative Example 4 A method for preparing a Co-doped nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in a vacuum at 60°C for 12 h to obtain a blue nickel-alanine complex.

[0078] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0079] S2, 0.25mg NiO xThe particles were mixed with 50 μL of ethanol and 2.5 μL of Nafion, and then ultrasonically dispersed. The mixture was coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0080] S3, using a three-electrode system with NiO x / carbon paper was used as the working electrode, graphite was used as the counter electrode, and Hg / HgO was used as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A pulse potential was applied to activate the nickel oxide. The pulse width was 1 s, the cathode potential was -1 V vs. RHE → the anode potential was 3 V vs. RHE, and the cycle was repeated 50 times to obtain a nickel oxide matrix.

[0081] S4. Prepare the electrolyte: A 0.15M Co(NO3)2 aqueous solution was used as the electrolyte. A three-electrode system was used, with nickel oxide substrate as the working electrode, graphite as the counter electrode, and saturated calomel electrode as the reference electrode. Constant potential electrochemical in situ deposition was performed at -1V vs. SCE for 20min to obtain a Co-doped nickel oxide-based catalyst, named Co-pNiO. x catalyst.

[0082] Comparative Example 5 A method for preparing nickel oxide particles comprises the following steps: Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuum at 60°C for 12 h to obtain a blue nickel-alanine complex.

[0083] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0084] Comparative Example 6 A method for preparing a nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0085] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0086] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0087] S3, using a three-electrode system with NiO x / carbon paper as the working electrode, graphite as the counter electrode and Hg / HgO as the reference electrode, with a 1 M potassium hydroxide solution as the electrolyte, an anodic potential was applied to the nickel oxide pulse activation, the anodic potential was 3 V vs. RHE, and a nickel oxide-based catalyst was obtained, named oNiO x catalyst.

[0088] Comparative Example 7 A method for preparing a nickel oxide-based catalyst comprises the following steps: S1. Dissolve 0.622 g of nickel acetate and 1.0 g of α-alanine in 10 mL of deionized water, stir at room temperature for 10 min until completely dissolved, add 140 mL of anhydrous ethanol, continue stirring for 5 min to form a blue suspension, centrifuge at 6000 rpm for 10 min, and dry the product obtained by centrifugation in vacuo at 60 ° C for 12 h to obtain a blue nickel-alanine complex.

[0089] The nickel-alanine complex was placed in a muffle furnace, heated to 600°C at a rate of 1°C / min, and calcined for 2 hours in an air atmosphere. After calcination, it was naturally cooled and then ground to obtain nickel oxide particles, named NiO x particles.

[0090] S2, 0.25mg NiO x The particles, 50 μL of ethanol and 2.5 μL of perfluorosulfonic acid polymer were mixed and ultrasonically dispersed, and then coated on a 0.5 cm × 0.5 cm carbon paper and dried at 60 ° C to obtain NiO x / carbon paper, NiO x The loading capacity is 1 mg / cm 2 .

[0091] S3, using a three-electrode system with NiO x / carbon paper as the working electrode, graphite as the counter electrode and Hg / HgO as the reference electrode, with a 1 M potassium hydroxide solution as the electrolyte, a cathode potential of -1 V vs. RHE was applied to the nickel oxide pulse activation to obtain a nickel oxide-based catalyst named rNiO x catalyst.

[0092] Comparative Example 8 Commercial noble metal catalyst RuO2.

[0093] The nickel-based catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 7 were subjected to structural and performance tests, and the results are as follows.

[0094] Figure 1 NiO was prepared in Comparative Example 5 of the present invention. x Particles and pNiO prepared in Comparative Example 6 x X-ray diffraction pattern of the catalyst. Figure 1 As shown, the pNiO prepared in Comparative Example 6 x The catalyst is NiO with a cubic crystal structure.

[0095] Figure 2 pNiO prepared in Comparative Example 6 of the present invention x The morphology of the catalyst, Figure 2 Figure a is a scanning electron microscope image, Figure b is a transmission electron microscope image, and Figure c is a high-angle annular dark field scanning transmission electron microscope image. Figure 2 As shown in Figures a and b, pNiO x The particle size of the catalyst is 30nm±5nm. Figure 2 As shown in Figure c, a composite shell layer consisting of about 5 nm amorphous Ni(OH)2 and NiOOH is formed on the surface.

[0096] Figure 3 Co2Fe1-pNiO prepared in Example 1 of the present invention x Catalyst, Co1Fe2-pNiO prepared in Example 2 x Catalyst, Comparative Example 3 Preparation of Fe-pNiO x Catalyst and Comparative Example 4 Preparation of Co-pNiO x Scanning electron micrograph of the catalyst. Figure 3 Figure a1 shows the Co2Fe1-pNiO prepared in Example 1 with a size of 200 nm. x Catalyst, Figure a2 shows the Co2Fe1-pNiO prepared in Example 1 at 1 μm size x Catalyst, Figure b1 shows the Co1Fe2-pNiO prepared in Example 2 at a size of 200 nm x Catalyst, Figure b2 shows Co1Fe2-pNiO prepared in Example 2 at 1 μm sizex Catalyst, Figure c1 shows Fe-pNiO prepared in Comparative Example 3 at 200nm size x Catalyst, Figure c2 shows Fe-pNiO prepared in Comparative Example 3 at 1 μm size x Catalyst, d1 shows Co-pNiO prepared in comparative example 4 at 200nm size x Catalyst, d2 is the Co-pNiO prepared in comparative example 4 at 1 μm size x Catalyst. Figure 3 As shown, compared to Figure 2 pNiO in Figure a x Morphology of Co2Fe1-pNiO prepared in Example 1 x Catalyst, Co1Fe2-pNiO prepared in Example 2 x Catalyst and Comparative Example 3 Preparation of Fe-pNiO x The morphology of the catalyst did not change, only the Co-pNiO prepared in Example 4 x Very thin flakes appeared on the surface of the catalyst, which may be OH separated by water during the electrodeposition process. - Combined with Co ions to form Co(OH)2.

[0097] Figure 4 Preparation of pNiO for Comparative Example 1 of the present invention x Catalyst, Comparative Example 5 Preparation of NiO x Catalyst, Comparative Example 6 Preparation of oNiO x Catalyst and Comparative Example 7 Preparation of rNiO x X-ray photoelectron spectroscopy of the catalyst, Figure 4 Figure a in the figure is Ni 2p 3 / 2 Spectrum, and b is the O 1s spectrum. Figure 4 As shown, for NiO x The peaks at 853.9eV, 855.4eV and 860.8eV correspond to Ni 2+ 、Ni 3+ and its satellite peaks. rNiO x Catalyst and pNiO x Ni in catalyst 2+ The peak area is significantly smaller than that of NiO x and oNiO x , which indicates that the reduction potential promotes the x Surface Ni 2+ To you 3+ Species transformation. NiO x The O 1s high-resolution XPS spectrum can be deconvoluted into three peaks: lattice oxygen O at 529.3 eV Ni-O, undercoordinated / hydroxyl oxygen O at 531.05 eV OH and adsorbed water oxygen O at 532.06 eV H2O . With NiO x Compared with the catalyst, oNiO x Catalyst, rNiO x Catalyst and pNiO x The catalyst exhibited greater O OH Peak area, indicating NiO x O in the surface layer Ni-O Converted to O OH Among them, pNiO x O OH The peak area is the largest, and its O OH The peak position shows a negative shift. These results indicate that NiO x The surface layer is transformed into a composite shell composed of amorphous Ni(OH)2 and NiOOH.

[0098] Figure 5 NiO was prepared in Comparative Example 5 of the present invention. x Catalyst and Comparative Example 6 Preparation of pNiO x Raman spectra of the catalyst and its comparative example. Figure 5 As shown, NiO x Catalyst at 503 cm -1 and 1059cm -1 The peaks at correspond to the first-order 1P-LO and second-order 2P-LO longitudinal optical modes, respectively. x The additional 1P-TO of the catalyst is shown at 384 cm -1 and 2P-TO such as 684cm -1 The peak indicates that the pulse potential induces the activation of the transverse optical mode. The emergence of the 1P-TO mode is attributed to the formation of surface defects such as interstitial oxygen, nickel vacancies and lattice distortion caused by the pulse treatment.

[0099] Figure 6 Co2Fe1-pNiO prepared in Example 1 of the present invention x Catalyst, Comparative Example 3 Preparation of Fe-pNiO x Catalyst, Comparative Example 4 Preparation of Co-pNiO x Catalyst and Comparative Example 6 Preparation of pNiO x X-ray photoelectron spectroscopy of the catalyst, Figure 6 Figure a is the O 1s spectrum, and Figure b is the Ni 2p spectrum. 3 / 2 Spectrum, Figure c is Co2Fe1-pNiO x Catalyst and Fe-pNiO x Fe 2p spectrum of the catalyst, d is Co2Fe1-pNiOx Catalyst and Co-pNiO x Co 2p spectrum of the catalyst. Figure 6 As shown in Figure a, the lattice oxygen peak O Ni-O The position is not shifted, indicating that Co / Fe has not been combined with pNiO x Lattice oxygen bonding. Hydroxyl oxygen peak O OH The positive shift of Co / Fe only interacts with pNiO x The hydroxyl groups in the amorphous layer undergo coordination. Figure 6 As shown in Figure b, the Ni peak position does not shift significantly after doping with Co / Fe, indicating that there is no significant electronic interaction between Co / Fe and Ni ions. Combined with the O 1s results, the possibility of direct bonding between Co / Fe and Ni is further excluded. Figure 6 As shown in Figure c, Co2Fe1-pNiO x The Fe binding energy of Fe-pNiO is higher than that of Fe-pNiO x The shift is negative by 0.9 eV, which indicates that the presence of Co induces the valence of Fe to decrease. Figure 6 As shown in Figure d, Co2Fe1-pNiO x China Co 3+ The peak shifted positively by 0.36 eV and the peak area increased significantly. The introduction of Fe promoted the 2+ To Co 3+ The oxidation of Co and Fe confirmed the existence of electron exchange between Co and Fe.

[0100] The nickel-based catalysts prepared in Examples 1 to 2 and Comparative Examples 1 to 7 and the commercial noble metal catalyst RuO2 in Comparative Example 8 were used to electrolyze water to produce oxygen, comprising the following steps: A three-electrode system was used, with the nickel-based catalyst prepared in the examples and comparative examples as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode. A 1 M potassium hydroxide solution was used as the electrolyte. A voltage was applied to the working electrode. The specific LSV curve test voltage range was: 1.1 V vs. RHE → 1.9 V vs. RHE, 10 mV / s. The specific stability curve test constant current density was: 10 mA / cm -2 .

[0101] Figure 7 The LSV curves of the catalysts prepared in Example 1 and Examples 3 to 5 are shown. At this time, the transition metal-doped nickel oxide-based catalyst prepared in Example 1 is named Co2Fe1-pNiO x -20, which is convenient for distinguishing from the catalysts prepared in Examples 3 to 5. Figure 7 As shown, in 1M KOH solution, Co2Fe1-pNiO prepared in Example 3 x-10 achieved 10 mA / cm at a low overpotential of 287 mV 2 Current density, better than pNiO x The improvement of activity is because the deposition of Co and Fe changes the electronic structure of Ni atoms in the composite shell composed of Ni(OH)2 and NiOOH, thereby optimizing its adsorption capacity for reaction intermediates. As the deposition time increases, the Co2Fe1-pNiO prepared in Example 1 x -20 shows an overpotential of 280mV, due to the further optimization of the electronic structure of Ni by appropriate amounts of Co and Fe. By further extending the deposition time, the Co2Fe1-pNiO prepared in Example 4 and Example 5 x -40 and Co2Fe1-pNiO x The overpotential at -80°C increased sharply, which may be due to the excessive Co and Fe ions covering the Ni active sites.

[0102] Figure 8 The LSV curves of the catalysts prepared in Examples 1 to 2 and Comparative Examples 1 to 8 are shown in FIG. Figure 8 As shown, in 1M KOH, NiO prepared in Comparative Example 5 x At 10 mA / cm 2 The overpotential at the current density is 570mV, while the pNiO prepared in Comparative Example 1 x The overpotential is 406 mV, and this reduction in overpotential is attributed to the x The stable Ni-O bond on the surface is broken, forming a composite shell composed of defect-rich amorphous Ni(OH)2 and NiOOH. Further doping pNiO with transition metal elements Co, Fe and Mn x It was found that Co2Fe1-pNiO obtained by co-doping Co and Fe x It has an extremely low overpotential of 280 mV, close to the 285 mV level of commercial precious metal RuO2, which may be attributed to the change of its surface composition and the electronic interaction between Co and Fe. This change in electronic structure potentially affects its adsorption and desorption ability of reaction intermediates.

[0103] Figure 9 The stability test curves of the catalysts of Example 1, Comparative Example 6 and Comparative Example 8 are shown in FIG. Figure 9As shown, in 1M KOH, the potential remained unchanged after 900 hours at a current density of 10 mA / cm², while the commercial RuO2 catalyst completely deactivated after 150 hours. As mentioned above, the noble metal replacement strategy offers: material costs far lower than commercial RuO2, without reliance on scarce resources such as Ir; a low-energy process: the total energy consumption of the electrochemical activation and co-deposition method is far lower than that of traditional high-temperature calcination methods; and environmental friendliness: the preparation process produces no toxic byproducts, and the electrolyte can be recycled with a recovery rate of >95%.

[0104] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although 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 understand the basic inventive concepts. 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.

[0105] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a transition metal-doped nickel oxide-based catalyst, characterized in that: The following steps are involved: Nickel oxide is loaded on a conductive substrate to form a working electrode, and a potassium hydroxide solution is used as the first electrolyte. The nickel oxide is pulse activated by a pulse potential method to induce oxygen vacancies and lattice distortion on the surface of the nickel oxide to obtain a nickel oxide matrix. The nickel oxide substrate is used as the working electrode, the transition metal salt solution is used as the second electrolyte, and the transition metal salts are soluble divalent cobalt salts and soluble trivalent iron salts. Electrochemical in-situ deposition is performed under a constant voltage to obtain a transition metal-doped nickel oxide-based catalyst.

2. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 1, wherein: The pulse potential method adopts a three-electrode system, the counter electrode is a graphite electrode, the reference electrode is Hg / HgO or Ag / AgCl, the pulse potential of the working electrode is -0.5V vs.RHE to -2V vs.RHE, the pulse potential of the counter electrode is 2V vs.RHE to 4V vs.RHE, the pulse width is 0.1s to 1s, and the pulse cycle parameters are 50 times to 300 times; the concentration of potassium hydroxide is 0.05M to 1M.

3. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 1, wherein: The loading of nickel oxide on the conductive substrate is 0.5 mg / cm 2 ~2mg / cm 2 , the conductive substrate is carbon paper, carbon cloth or nickel foam.

4. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 1, wherein: The total concentration of transition metal ions in the transition metal salt solution is 0.1M-0.3M, and the molar ratio of the soluble divalent cobalt salt to the soluble trivalent iron salt is 1:0.2-2.

5. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 1, wherein: The potential of the constant voltage is -0.5 V vs. SCE to -2 V vs. SCE, the deposition temperature is room temperature, and the deposition time is 10 min to 80 min.

6. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 1, wherein: The preparation method of nickel oxide comprises the following steps: A soluble nickel salt and a complexing agent are dissolved in a solvent to form a complex, and then an alcohol inducer is added to induce precipitation of the complex to obtain a nickel complex; The nickel complex is calcined at 400° C. to 600° C. to obtain nickel oxide.

7. The method for preparing a transition metal-doped nickel oxide-based catalyst according to claim 6, wherein: The molar ratio of the soluble nickel salt to the complexing agent is 1:1-3, the complexing agent is α-alanine, the volume ratio of the alcohol inducer to the solvent is 10-15:1, and the alcohol inducer is ethanol, isopropanol or methanol; the calcination heating rate is 1°C / min-5°C / min, and the calcination holding time is 1h-6h.

8. A transition metal-doped nickel oxide-based catalyst, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. The transition metal-doped nickel oxide-based catalyst according to claim 8, characterized in that The transition metal-doped nickel oxide-based catalyst uses a conductive substrate as a carrier, the carrier loads a nickel oxide matrix, the surface of the nickel oxide matrix loads a composite shell layer, the composite shell layer is composed of amorphous Ni(OH)2 and NiOOH, the surface of the composite shell layer is doped with transition metal elements, and the doping amount of the transition metal elements is 1% to 10% of the atomic ratio of the composite shell layer surface, wherein the crystal form of the nickel oxide matrix is ​​cubic phase, the particle size range of the nickel oxide matrix is ​​20nm to 100nm, and the thickness of the composite shell layer is 1nm to 10nm.

10. Use of the transition metal-doped nickel oxide-based catalyst according to claim 9 in electrocatalytic water decomposition.

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