CN113502494B - High-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite and preparation and application thereof - Google Patents

High-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite and preparation and application thereof Download PDF

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CN113502494B
CN113502494B CN202110575237.2A CN202110575237A CN113502494B CN 113502494 B CN113502494 B CN 113502494B CN 202110575237 A CN202110575237 A CN 202110575237A CN 113502494 B CN113502494 B CN 113502494B
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coo
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cobalt oxide
oxygen vacancy
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CN113502494A (en
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郑灵霞
杨鹏举
郑华均
王永智
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Zhejiang University of Technology ZJUT
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Abstract

A high valence state metal ion doped oxygen vacancy-rich cobalt oxide nano composite material is prepared by the following steps: mixing a mixed aqueous solution of cobalt salt and metal M salt (M ═ Mo or W) with a urea aqueous solution to obtain a precursor solution, adding the precursor solution into a pretreated foamed nickel substrate, reacting at 90-160 ℃ for 1-12 h to obtain a precursor material on the foamed nickel substrate, and mixing the precursor material with NaBH4Putting the mixture into a tube furnace, heating the mixture to 300-350 ℃ under the protection of inert gas, and calcining the mixture for 2-9 hours to obtain the catalyst; according to the invention, a metal cation doping and oxygen vacancy introducing mode is adopted, the electronic structure and the carrier concentration of the material are effectively regulated and controlled, and the intrinsic conductivity and the diversity of redox reactions of the material are improved; the micro-morphology of the composite nano material is further adjusted, the specific surface area of the composite nano material is increased, and the transmission path of ions is effectively shortened; the material is used as an oxygen evolution reaction electrode, and shows excellent oxygen evolution catalytic performance and stability in an alkaline system.

Description

High-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite and preparation and application thereof
Technical Field
The invention belongs to the technical field of nano-structure functional materials and electrocatalytic oxygen evolution, and particularly relates to high-valence metal ion doped cobalt oxide (written as M/CoO) rich in oxygen vacancyxMetal cation M is Mo, W) nano composite material, a preparation method thereof and application thereof in electrocatalytic oxygen evolution reaction.
Background
In order to overcome the dependence on the conventional fossil fuel and alleviate the problem of environmental pollution, the development of renewable clean energy is imperative. Hydrogen energy is regarded as the most potential clean energy source due to the advantages of extremely high energy density, high-efficiency heat conversion efficiency, zero pollution of combustion products and the like. Among various hydrogen production technologies, the electrocatalytic water splitting is an important means for industrial hydrogen production, has the characteristics of zero emission, high hydrogen production purity and capability of coupling renewable energy sources such as solar energy, wind energy, nuclear energy and the like, and is also an optimal way for hydrogen economy.
The hydrogen production by water electrolysis mainly comprises two half reactions of a cathodic Hydrogen Evolution Reaction (HER) and an anodic Oxygen Evolution Reaction (OER), and compared with a double-electron transfer process of the HER, the OER relates to a complex reaction process involving four electrons and multiple intermediate products, is a kinetic retardation process and needs higher overpotential, so that the efficiency of the whole water electrolysis process is very low; and the introduction of the high-efficiency OER catalyst can obviously reduce the kinetic barrier and improve the speed of oxygen evolution from electrolyzed water. Typically, noble metal oxides (e.g., RuO)2And IrO2) Has high catalytic activity and stability in both acidic and basic environments, and is considered as a reference electrocatalyst of OER. However, their scarcity and high cost are major obstacles that limit practical applications. In view of this, the development of a high-efficiency low-cost non-noble metal OER electrocatalyst is urgently needed to reduce the reaction overpotential and improve the energy conversion efficiency.
In recent years, transition metal oxides have been attracting attention because of their low cost and excellent catalytic activity. Among them, cobalt oxide has been widely used in the electrochemical field due to its excellent redox activity and environmental friendliness, but is limited by its low intrinsic conductivity and limited reactive sites, and its electrochemical performance needs to be further improved. Doping is a common method for adjusting the carrier concentration and conductivity of a material, and the change of the chemical composition of the material can effectively adjust and control the electronic structure of the material, so that the intrinsic conductivity is optimized. A great deal of research shows that proper doping of transition metal can improve the performance of the catalyst from the aspects of conductivity, reaction energy barrier, electrochemical active area, active site and the like, in particular toHigh valence non-3 d transition metal ion (Mo)6+，W6+) The electrocatalytic stability of the material can be obviously improved by the doping. On the other hand, the existence of vacancy defects enables the electrocatalyst to expose more coordination unsaturated sites and dangling bonds, so that the electron density near the Fermi level can be effectively adjusted, and the electrocatalytic performance is further optimized.
However, the strategy of combining both doped and vacancy defect structures is also less in the preparation of electrocatalyst materials. In view of the above, the invention provides a cobalt oxide composite nanomaterial (M/CoO) with high valence metal ions doped with oxygen-rich vacancyxM ═ Mo or W), the microstructure of the material has adjustability, and the material can provide larger specific surface area and abundant redox reaction sites; the doping of the second metal and the introduction of oxygen vacancies effectively regulate and control the electronic structure of the cobalt oxide and improve the intrinsic conductivity of the material. Under an alkaline system, the material has excellent electrocatalytic performance and effectively shortens an ion transmission path.
Disclosure of Invention
The invention aims to provide a high-valence metal ion doped oxygen vacancy-rich cobalt oxide composite nano material (recorded as M/CoO)xThe metal cation M is Mo or W), and the metal cation M is used as an electrode in a half-reaction oxygen evolution reaction of electrolyzed water.
According to the invention, a metal cation doping and oxygen vacancy introducing mode is adopted, the electronic structure and the carrier concentration of the material are effectively regulated and controlled, and the intrinsic conductivity and the diversity of redox reactions of the material are improved; the micro-morphology of the composite nano material is further adjusted, the specific surface area of the composite nano material is increased, and the transmission path of ions is effectively shortened.
The preparation method of the composite nano material has the advantages of simple process, short time consumption, low cost and the like. The material is used as an oxygen evolution reaction electrode, shows excellent oxygen evolution catalytic performance and stability in an alkaline system, and is expected to become a new electro-catalytic material.
The technical scheme of the invention is as follows:
a high-valence metal ion doped cobalt oxide nano composite material rich in oxygen vacancies is prepared by the following method:
(1) mixing a mixed aqueous solution of cobalt salt and metal M salt with a urea aqueous solution to obtain a precursor solution, adding the precursor solution into a pretreated foamed nickel substrate, reacting at 90-160 ℃ for 1-12 h, taking out foamed nickel, washing and drying to obtain a precursor material on the foamed nickel substrate;
the cobalt salt is cobalt nitrate, cobalt chloride or cobalt acetate;
the metal M salt is molybdenum (Mo) salt or tungsten (W) salt; the molybdenum salt is sodium molybdate or ammonium molybdate; the tungsten salt is sodium tungstate or tungsten chloride;
in the mixed aqueous solution of the cobalt salt and the metal M salt, the concentration of the cobalt salt is 50-150 mmol/L, and the concentration of the metal M salt solution is 5-40 mmol/L;
the concentration of the urea aqueous solution is 500-600 mmol/L;
the volume ratio of the mixed aqueous solution of the cobalt salt and the metal M salt to the urea aqueous solution is 1: 1;
the pretreatment method of the foamed nickel substrate comprises the following steps: sequentially cleaning a foamed nickel substrate with acetone, deionized water (DI), 3M hydrochloric acid, deionized water and absolute ethyl alcohol for 15min under an ultrasonic condition, and drying in vacuum for later use;
(2) the foam nickel substrate loaded with the precursor material obtained in the step (1) and NaBH4Placing the mixture into a tubular furnace, heating the mixture to 300-350 ℃ under the protection of inert gas, and calcining the mixture for 2-9 hours to obtain the high-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite;
the NaBH4The mass ratio of the precursor material to the precursor material is 20-200: 1;
the inert gas is nitrogen, argon or helium, preferably nitrogen;
the heating rate of the calcination is 2 ℃/min.
According to the method, a metal salt dopant of molybdenum or tungsten, cobalt salt and urea are used as reaction raw materials, deionized water is used as a solvent, foam nickel is used as a substrate, a constant-temperature hydrothermal method is adopted to directly dope metal cations into a cobalt salt-containing material instead of part of cobalt, and the shape of a nano material is adjusted; then under the protection of inert gasSodium borohydride (NaBH) then4) Calcining in reducing atmosphere to obtain final product M/CoOx。
The invention optimizes the morphology and electronic structure of the material by adjusting metal cations M (molybdenum or tungsten) to replace part of Co, thereby improving the active sites and conductivity of the electrode material.
The high-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite prepared by the invention can be used as an electrode material to be applied to a half-reaction oxygen evolution reaction of electrolyzed water.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, a hydrothermal method is adopted, high-valence metal cations M are directly doped in a Co precursor growing on foam nickel in situ to replace partial cobalt atoms, the micro morphology of the material is adjusted, and the specific surface area and the porosity of the catalytic material are greatly improved; the second metal is introduced and reduced and calcined to manufacture oxygen vacancies, so that the diversity of redox reactions is increased, the electronic structure is optimized, and finally the oxygen evolution performance of the material is greatly improved.
The composite nano material has a two-dimensional ultrathin nano sheet stacked multilevel structure, and the specific surface area of the composite nano material is not less than 120m2 g-1The method is beneficial to providing more redox reaction sites and effectively shortening the ion transmission path. The doping agent is a molybdenum source or a tungsten source, exists in the form of the highest valence metal ions (+6), the doping atom percentage is 3.5-20%, and meanwhile, the cobalt-based composite material is rich in oxygen vacancies, so that the electronic structure of the cobalt oxide material can be effectively regulated and controlled, and the intrinsic conductivity is improved.
The preparation method of the composite nano material has the advantages of simple process, good reproducibility, low cost, environmental friendliness and the like. The prepared M/CoOxThe composite nano material is used for electrocatalytic oxygen evolution reaction, shows lower overpotential in alkaline solution and has wider application prospect. Notably, this is also M/CoOxThe method is applied to the field of electrocatalytic oxygen evolution for the first time.
Drawings
FIG. 1 shows the results obtained in example 1CoOxScanning electron microscope images of the electrode material under different magnifications.
FIG. 2 shows CoO obtained in example 1xX-ray diffraction pattern of the electrode material.
FIG. 3 shows the W/CoO obtained in example 2x-1 electron microscope scan of electrode material at different magnifications.
FIG. 4 shows Mo/CoO obtained in example 3x-2 electron micrographs of the electrode material at different magnifications.
FIG. 5 is the Mo/CoO obtained in example 3x-2 AFM images of the material.
FIG. 6 is the Mo/CoO obtained in example 3x-2X-ray diffraction pattern of the electrode material.
FIG. 7 shows Mo/CoO obtained in example 3x-XPS plot of material Mo 3 d.
FIG. 8 is the Mo/CoO obtained in example 3x-2 transmission electron micrographs of the electrode material at different magnifications.
FIG. 9 shows CoO obtained in examples 1 and 3xAnd Mo/CoOx-2O 1s XPS and EPR profiles of material.
FIG. 10 shows Mo/CoO obtained in example 4x-3 scanning electron micrographs of the electrode material at different magnifications.
FIG. 11 is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-BET and BJH plots of 3.
FIG. 12 shows CoO obtained in examples 1, 2, 3 and 4x，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-3 electrochemical performance diagram of electrode material.
Detailed Description
The invention is further described below by means of specific examples, without the scope of protection of the invention being limited thereto.
Example 1: CoOxPreparation and oxygen evolution performance (undoped high valence state metal ion)
Dissolving cobalt nitrate (0.582g, 2mmol) in 20mL DI, dissolving urea (0.6g, 10mmol) in 20mL DI, mixing the two solutions uniformly, and transferring the solution to a 50mL hydrothermal kettle; the pretreated 4X 1cm nickel foam matrix was added and reacted at 120 ℃ for 6 hours. And naturally cooling to room temperature after the reaction is finished, taking out the foamed nickel matrix, washing the foamed nickel matrix with deionized water and absolute ethyl alcohol for a plurality of times, and carrying out vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the precursor material.
Placing the prepared foamed nickel (loaded with 0.01g of precursor material) in a porcelain boat, and weighing 1.0g of NaBH4Placing in another porcelain boat. Loaded with NaBH4The ceramic boat is arranged at the upstream, and the ceramic boat filled with the foamed nickel is arranged in the middle section of the tube furnace. Heating to 350 ℃ at the speed of 2 ℃/min under the nitrogen atmosphere and preserving the heat for 2 hours to obtain the CoOxAnd (3) sampling.
FIG. 1 is a CoO obtained in example 1xScanning electron microscope images of the material at different magnifications. FIG. 1a clearly shows that the sample we have obtained is a morphology composed of one-dimensional nanowires and two-dimensional nanoplates together, which are cross-linked to the nanowires (FIGS. 1 b-c).
FIG. 2 shows CoO obtained in example 1xX-ray diffraction pattern of the material. As can be seen from the figure, CoOxThe spectrum of the sample can be divided into Co3O4(JCPDS No.43-1003), CoO (JCPDS No.70-2855) and Co (JCPDS No. 05-0727). The three strong peaks at 2 θ values of 36.8 °, 42.8 ° and 62.2 ° correspond to the (111), (200) and (220) facets of CoO, while the peaks at 2 θ values of 47.5 ° and 75.9 ° correspond to the (101) and (110) facets of Co.
Example 2: W/CoOxPreparation of (1) and oxygen evolution Properties
Dissolving cobalt chloride (0.582g, 2.45mmol) and sodium tungstate (0.04g, 0.12mmol) in 20mL DI, dissolving urea (0.6g, 10mmol) in 20mL DI, mixing the two uniformly, and transferring the solution to a 50mL hydrothermal kettle; the pretreated 4X 1cm nickel foam matrix was added and reacted at 120 ℃ for 6 hours. And naturally cooling to room temperature after the reaction is finished, taking out the foamed nickel matrix, washing the foamed nickel matrix with deionized water and absolute ethyl alcohol for a plurality of times, and carrying out vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the precursor material.
Placing the prepared foamed nickel (loaded with 0.007g of precursor material) in a porcelain boatWeighing 1.0g NaBH4Placing in another porcelain boat. Loaded with NaBH4The ceramic boat is arranged at the upstream, and the ceramic boat filled with the foamed nickel is arranged in the middle section of the tube furnace. Heating to 350 ℃ at the speed of 2 ℃/min under the nitrogen atmosphere and preserving the heat for 2 hours to obtain the W/CoOx-1 sample.
FIG. 3 is the W/CoO obtained in example 2x-1 scanning electron microscope images of the material at different magnifications. Comparing with fig. 1, we can clearly see that with the addition of a small amount of sodium tungstate, the morphology of the nanomaterial is changed significantly. The content of the nano-sheets is greatly increased, and the number of the nano-wires is reduced, which proves that the addition of the tungsten source has obvious effect on changing the appearance of the nano-material.
Example 3: Mo/CoOxPreparation of (E) -2 and oxygen evolution Properties thereof
Dissolving cobalt acetate (0.582g, 2.3mmol) and sodium molybdate (0.12g, 0.5mmol) in 20mL DI, dissolving urea (0.6g, 10mmol) in 20mL DI, mixing the two uniformly, and transferring the solution to a 50mL hydrothermal kettle; the pretreated 4X 1cm nickel foam matrix was added and reacted at 120 ℃ for 6 hours. And naturally cooling to room temperature after the reaction is finished, taking out the foamed nickel matrix, washing the foamed nickel matrix with deionized water and absolute ethyl alcohol for a plurality of times, and carrying out vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the precursor material.
Placing the prepared foamed nickel (loaded with 0.008g of precursor material) in a porcelain boat, and weighing 1.0g of NaBH4And placing the ceramic boat in another ceramic boat. Loaded with NaBH4The ceramic boat is arranged at the upstream, and the ceramic boat filled with the foamed nickel is arranged at the middle section of the tube furnace. Heating to 350 ℃ at the speed of 2 ℃/min under the nitrogen atmosphere, and preserving the heat for 2 hours to obtain the Mo/CoOx-2 samples.
FIG. 4 shows Mo/CoO obtained in example 3x-2 scanning electron microscope images of the material at different magnifications. Compared with fig. 1 and fig. 3, we can clearly see that the microscopic morphology of the material is completely converted into a three-dimensional nanosheet network structure composed of ultrathin two-dimensional nanosheets from the coexistence of the nanowires and the nanosheets. The ultrathin nanosheet has a very smooth surface and a large specific surface area, which is beneficial to the permeation and ion transmission of electrolyte and improves the electrochemistry thereofAnd (4) performance.
FIG. 5 is the Mo/CoO obtained in example 3xAFM image of-2 Material, Mo/CoO can be seenxThe thickness of-2 nano-sheets is less than 2nm, and the ultra-thin characteristics are realized.
FIG. 6 is the Mo/CoO obtained in example 3x-2X-ray diffraction pattern of the material. As can be seen from the figure, Mo/CoOxThe spectrum of the-2 sample can be divided into CoO (JCPDS No.42-1300) and CoO (JCPDS No. 70-2855). No diffraction peak of the molybdenum compound was found in the XRD result, indicating that no molybdenum compound phase was formed during the doping.
FIG. 7 shows Mo/CoO obtained in example 3x-2 XPS plot of Mo material, from which it can be analyzed, Mo/CoOxDeconvolution of Mo 3d spectra from-2 shows Mo 3d3/2(235.5eV) and Mo 3d5/2Two peaks (232.2eV) indicating the high valence of Mo (+ 6).
FIGS. 8a-d are Mo/CoO obtained in example 3x-2 transmission electron microscope images of the material at different magnifications. The ultrathin nanosheet structure can be clearly seen, and the nanosheets are provided with a plurality of penetrating open pores, so that transmission of ions is facilitated, and the result of a transmission electron microscope is well matched with the result of a scanning electron microscope. In addition, we also judge that the nanomaterial consists of two different crystalline phases of CoO together by lattice fringes. FIG. 8e is an energy dispersive X-ray spectroscopy (EDS) of the sample showing a uniform distribution of Co, Mo, C, N, O elements.
FIG. 9 is the CoO obtained in examples 1 and 3xAnd Mo/CoOx-2O 1s XPS and EPR profiles of material. The O1s diagram consists of three oxygen peaks, lattice oxygen (O1) at 530.1eV, surface adsorbed water molecules (O3) at 532.7eV, and defect oxygen (O2) at 531.6 eV. The oxygen-rich vacancy is derived from NaBH4Strong reduction of (2). Impressively, Mo/CoO x2 has a ratio CoOxHigh oxygen vacancies, stronger peak intensity (O2). In addition, EPR can examine unpaired electrons in defect-related species and vacancies. Co3O4，CoOxAnd Mo/CoOx-2 composite shows a symmetric EPR signal at g-2.002. And Co3O4Compared with that ofCoO was readily observedxAnd Mo/CoOxThe peak intensity of-2 is higher, which is consistent with the O1s XPS results. CoOxAnd Mo/CoOxThe prominent resonance line of the paramagnetic phase of the-2 composite in the EPR absorption spectrum shows that NaBH4And the presence of oxygen vacancies.
Example 4: Mo/CoOxPreparation of (E) -3 and oxygen evolution Properties thereof
Dissolving cobalt acetate (0.582g, 2mmol) and ammonium molybdate (0.24g, 0.2mmol) in 20mL DI, dissolving urea (0.6g, 10mmol) in 20mL DI, mixing the two uniformly, and transferring the solution to a 50mL hydrothermal kettle; the pretreated 4X 1cm nickel foam matrix was added and reacted at 120 ℃ for 6 hours. And naturally cooling to room temperature after the reaction is finished, taking out the foamed nickel matrix, washing the foamed nickel matrix with deionized water and absolute ethyl alcohol for a plurality of times, and carrying out vacuum drying for 12 hours at the temperature of 60 ℃ to obtain the precursor material.
Placing the prepared foamed nickel (loaded with 0.008g of precursor material) in a porcelain boat, and weighing 1.0g of NaBH4Placing in another porcelain boat. Loaded with NaBH4The ceramic boat is arranged at the upstream, and the ceramic boat filled with the foamed nickel is arranged in the middle section of the tube furnace. Heating to 350 ℃ at the speed of 2 ℃/min under the nitrogen atmosphere and preserving the heat for 2 hours to obtain the Mo/CoOx-3 samples.
FIG. 10 is the Mo/CoO obtained in example 4x-3 scanning electron microscope images of the material at different magnifications. In comparison with FIGS. 1, 3 and 4, it can be clearly seen that Mo/CoO increases with the molybdenum salt concentrationxIs formed by the 3D nanoflower and the 2D nanosheet array together.
FIG. 11 is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOxBET and BJH plot of-3, it can be seen that CoO when there is no Mo or W dopingxThe specific surface area and the number of pores are minimized. As the amount of Mo or W doping increases, the specific surface area increases and then decreases, which can also be inferred from SEM images. The morphology of the material is firstly changed from one dimension to two dimensions, and the specific surface area is increased. Finally, the specific surface area is correspondingly reduced from two-dimensional change to three-dimensional change.
FIG. 12a is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-3 LSV curve of electrode material in 1M KOH solution. It can be seen that the current density was 10mA/cm2In time of Mo/CoOxOverpotential of-2 electrode 260mV higher than CoOx，W/CoOx-1 and Mo/CoOx-3 properties. The ultrathin two-dimensional lamellar structure exposes more active sites, so that the ion transmission is facilitated; and the addition of the second metal also increases the diversity of the redox reaction.
FIG. 12b is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-Tafel curve of 3 electrodes in 1M KOH solution. The slope of the Tafel curve is 102mF · dec-1，150mF·dec-1，63mF·dec-1And 118mF dec-1This further indicates that the ultrathin sheet layer structure can accelerate the electron transport rate.
FIG. 12c is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-3 electrode electrochemical specific surface area histogram in 1M KOH solution. It can be seen that the electrochemical specific surface areas of the 4 electrodes are 26.4mF · dec, respectively-1，34.5mF·dec-1，68.3mF·dec-1， 64.8mF·dec-1Further, the two-dimensional structure has a larger electrochemical effective area.
FIG. 12d is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-3 electrochemical impedance spectroscopy of the electrode in 1M KOH solution. The Mo/CoO can also be seen from the figurex2 has smaller impedance, which shows that the charge transfer kinetics on the interface of the electrocatalyst and the electrolyte is faster, and finally the catalytic performance is greatly improved.
Table 1 is CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOxICP content analysis of-3. CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOxThe contents of W or Mo in-3 were 0, 3.82%, 16.36%, 18.59%, respectively.
TABLE 1
Figure BDA0003084099100000051
It can be seen from the above examples that the preparation method of the present invention is a relatively universal method, the amount of doped metal salt is controlled to control the micro-morphology of the nanomaterial and obtain the precursor, and the precursor is calcined in sodium borohydride under the protection of inert gas to finally obtain CoOx，W/CoOx-1，Mo/CoOx-2 and Mo/CoOx-3 samples, all of which show better oxygen evolution performance in alkaline solutions.

Claims (9)

1. The high valence state metal ion doped oxygen vacancy-rich cobalt oxide nano composite material is characterized by being prepared by the following method:
(1) mixing a mixed aqueous solution of cobalt salt and metal M salt with a urea aqueous solution to obtain a precursor solution, adding the precursor solution into a pretreated foamed nickel substrate, reacting at 90-160 ℃ for 1-12 h, taking out foamed nickel, washing and drying to obtain a precursor material on the foamed nickel substrate;
the metal M salt is molybdenum salt or tungsten salt;
(2) the foam nickel substrate loaded with the precursor material and NaBH which are obtained in the step (1) are added4And putting the mixture into a tubular furnace, heating to 300-350 ℃ under the protection of inert gas, and calcining for 2-9 h to obtain the high-valence metal ion doped cobalt oxide nanocomposite rich in oxygen vacancies.
2. The high-valence metal ion-doped oxygen vacancy-rich cobalt oxide nanocomposite material of claim 1, wherein in the step (1), the cobalt salt is cobalt nitrate, cobalt chloride or cobalt acetate.
3. The high valence metal ion doped oxygen vacancy rich cobalt oxide nanocomposite of claim 1, wherein in step (1), the molybdenum salt is sodium molybdate or ammonium molybdate.
4. The high valence metal ion doped oxygen vacancy rich cobalt oxide nanocomposite material of claim 1, wherein in step (1), the tungsten salt is sodium tungstate or tungsten chloride.
5. The high valence state metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite material of claim 1, wherein in the step (1), in the mixed aqueous solution of cobalt salt and metal M salt, the concentration of cobalt salt is 50-150 mmol/L, and the concentration of metal M salt solution is 5-40 mmol/L; the concentration of the urea aqueous solution is 500-600 mmol/L; the volume ratio of the mixed aqueous solution of the cobalt salt and the metal M salt to the urea aqueous solution is 1: 1.
6. the high-valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite material of claim 1, wherein in the step (1), the pretreatment method of the foamed nickel substrate comprises: and sequentially cleaning the foamed nickel substrate with acetone, deionized water, 3M hydrochloric acid, deionized water and absolute ethyl alcohol for 15min under an ultrasonic condition, and drying in vacuum for later use.
7. The high valence metal ion doped oxygen vacancy-rich cobalt oxide nanocomposite of claim 1, wherein in step (2), the NaBH4The mass ratio of the precursor material to the precursor material is 20-200: 1.
8. the high-valence metal ion-doped oxygen vacancy-rich cobalt oxide nanocomposite material of claim 1, wherein in the step (2), the temperature increase rate of the calcination is 2 ℃/min.
9. The use of the high valence metal ion doped oxygen vacancy rich cobalt oxide nanocomposite as an electrode material in a semi-reactive oxygen evolution reaction of electrolyzed water according to claim 1.
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