CN113667993B - Oxygen vacancy-rich cobalt monoxide/cobalt ferrite nanosheet array structure catalyst and preparation and application thereof - Google Patents
Oxygen vacancy-rich cobalt monoxide/cobalt ferrite nanosheet array structure catalyst and preparation and application thereof Download PDFInfo
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Abstract
Oxygen vacancy-rich CoO/CoFe 2 O 4 The catalyst with the nanosheet array structure is prepared by the following method: mixing a mixed solution of cobalt salt and ferric salt with an organic ligand solution, adding the mixed solution into a pretreated foamed nickel substrate, carrying out hydrothermal reaction for 1-6 h at 100-140 ℃, taking out the foamed nickel, and washing and drying to obtain a precursor material on the foamed nickel substrate; putting the obtained foam nickel loaded with the precursor material into a tubular furnace, simultaneously putting reducing agent sodium borohydride powder, heating to 250-450 ℃ under the protection of inert gas, calcining for 0.5-4.5 h to obtain CoO/CoFe 2 O 4 A nanosheet array structure catalyst; the preparation method has the advantages of simple operation, good reproducibility, low cost and environmental protection, and the prepared CoO/CoFe 2 O 4 The catalyst material is used for oxygen evolution reaction, shows lower overpotential in alkaline solution and has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of nano-structure functional materials and electrocatalytic oxygen evolution, and relates to cobalt monoxide/cobalt ferrite (CoO/CoFe) rich in oxygen vacancies 2 O 4 ) A catalyst with a nano-sheet array structure, a preparation method thereof and application thereof in electrocatalytic oxygen evolution reaction.
Background
The rapid depletion of fossil energy has stimulated the exploration of clean and sustainable energy storage and conversion technologies. For the moment, the electrically driven water splitting to produce hydrogen and oxygen is considered to be one of the most advantageous options to achieve clean renewable energy. Among them, oxygen Evolution Reaction (OER) is attracting attention because it plays an important role in the conversion and storage of a new generation of renewable energy such as regenerative fuel cells, rechargeable metal oxide batteries, water splitting, and the like. However, the inherent slow kinetics of OER severely hamperThe development of the energy technology is advanced. To improve reaction kinetics, efficient electrocatalysts are needed to overcome the reaction energy barrier and ensure fast electron and mass transport, thus improving energy efficiency. The most advanced current OER electrocatalytically active materials are noble metal oxides (e.g., irO) 2 /RuO 2 ) Its reserves are limited and expensive, greatly restricting large-scale commercial applications. Therefore, there is an urgent need to develop and design efficient low cost non-noble metal electrocatalysts.
Among the various non-noble metal catalysts, 3d transition metal oxides/hydroxides (Fe, co, ni, etc.) are considered to be the most common and stable OER catalysts in basic media, but their electrocatalytic performance is greatly limited by the disadvantage of their poor electrical conductivity. Defect engineering is considered to be one of the most effective methods for improving the electronic structure and physicochemical properties of materials. The reasonable construction of the defects not only facilitates ion diffusion and charge transfer, but also provides more abundant reactive sites for metal ions or intermediates, and can improve the flexibility and stability of the material, thereby playing a crucial role in improving the overall electrochemical performance. Oxygen Vacancy (Oxygen Vacancy) is the most common anion defect, and the Oxygen atom is absent, so that more dangling bonds are generated to change the electronic structure of the material, the conductivity of the material is improved, the rapid transmission of electrons is accelerated, and OH is facilitated - The adsorption of (2) accelerates the OER kinetic process, thereby improving the electrocatalytic activity. In addition, the presence of the bimetal may diversify the redox reaction compared to the monometallic compound and produce a synergistic effect of the metal cations, further improving the catalytic activity and stability of the electrocatalyst.
The Metal Organic Frameworks (MOFs) are porous crystalline materials formed by connecting metal ions/clusters and multifunctional organic ligands, and have an open crystal structure, excellent porosity, a flexible structure and an adjustable function. The preparation method comprises the steps of taking a cobalt-iron bimetallic organic framework material as a precursor, introducing oxygen vacancies by a calcination method in a protective atmosphere containing a reducing agent, and preparing an oxygen vacancy-rich cobalt-iron bimetallic oxide nanosheet array structure electrocatalyst composite material CoO/CoFe 2 O 4 In alkaline formIn addition, the material has excellent electrocatalytic oxygen evolution performance and catalytic stability.
Disclosure of Invention
The invention provides CoO/CoFe rich in oxygen vacancies 2 O 4 The catalyst with the nano-sheet array structure and the preparation method thereof are applied to the electrocatalytic oxygen evolution reaction.
The invention takes a cobalt-iron bimetallic framework compound as a precursor, introduces oxygen vacancy in an inert gas atmosphere containing a reducing agent in a calcining manner, and prepares CoO/CoFe rich in the oxygen vacancy 2 O 4 An electrocatalyst material with a nanosheet array structure. The introduction of oxygen vacancies effectively regulates and controls the electronic structure and the carrier concentration of the metal oxide material, and improves the intrinsic conductivity and the diversity of redox reactions. Meanwhile, the electrocatalytic activity is further optimized due to the synergistic effect of the bimetal.
The preparation method 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 catalytic stability in an alkaline system, and is expected to become a new electrocatalyst material.
The technical scheme of the invention is as follows:
oxygen vacancy-rich CoO/CoFe 2 O 4 The catalyst with the nanosheet array structure is prepared by the following method:
(1) Mixing a mixed solution of cobalt salt and ferric salt with an organic ligand solution, adding the mixed solution into a pretreated foamed nickel substrate, carrying out hydrothermal reaction for 1-6 h at 100-140 ℃, taking out the foamed nickel, and washing and drying to obtain a precursor material (marked as CoFe-MOF) on the foamed nickel substrate;
in the mixed solution of the cobalt salt and the ferric salt, the concentration of the cobalt salt is 100-120 mmol/L, and the molar ratio of the cobalt salt to the ferric salt is 1: 0.04-0.08, and the solvent is methanol or acetone;
the concentration of the organic ligand solution is 100-400 mmol/L, and the solvent is methanol or acetone;
the volume ratio of the mixed solution of the cobalt salt and the ferric salt to the organic ligand solution is 1:1;
the cobalt salt is selected from any one of cobalt nitrate, cobalt chloride and cobalt acetate;
the ferric salt is selected from any one of ferric chloride, ferric nitrate and ferric sulfate;
the organic ligand is dimethyl imidazole, terephthalic acid or phthalic acid;
the foamed nickel substrate is pretreated before use as follows: sequentially cleaning the mixture by using acetone, deionized water, 3M hydrochloric acid, deionized water and absolute ethyl alcohol for 15 minutes under an ultrasonic condition, and drying the mixture in vacuum for later use;
(2) Putting the foamed nickel loaded with the precursor material obtained in the step (1) into a tubular furnace, simultaneously putting reducing agent sodium borohydride powder, heating to 250-450 ℃ under the protection of inert gas (such as nitrogen, argon or helium), and calcining for 0.5-4.5 h to obtain CoO/CoFe 2 O 4 A catalyst with a nano-sheet array structure.
CoO/CoFe prepared by the invention 2 O 4 The catalyst with the nanosheet array structure can be applied to electrolytic water-based oxygen evolution reaction.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, a CoFe bimetal organic framework material precursor with a porous network structure and composed of nanosheets directly grows in situ on a foamed nickel substrate by adopting a solvothermal method, the microstructure and morphology of the material are regulated and controlled, and the specific surface area and the porosity are increased; and then, sodium borohydride powder is used as a reducing agent, and an oxygen vacancy is introduced by a calcination method under the protection of inert gas, so that the diversity of redox reactions is increased, the electronic structure is effectively regulated and controlled, the intrinsic conductivity is improved, and further the oxygen evolution performance of the material is greatly improved.
The preparation method has the advantages of simple operation, good reproducibility, low cost and environmental protection. The prepared CoO/CoFe 2 O 4 The catalyst material is used for oxygen evolution reaction, shows lower overpotential in alkaline solution and has wider application prospect.
Drawings
FIG. 1 is the CoO/CoFe obtained in example 1 2 O 4 -1 Scanning Electron Micrograph (SEM) of the electrode material.
FIG. 2 shows CoO/CoFe obtained in example 1 2 O 4 -1 Transmission Electron Micrograph (TEM) of the electrode material.
FIG. 3 shows CoO/CoFe obtained in example 1 2 O 4 -1X-ray diffraction pattern (XRD) of the electrode material.
FIG. 4 shows CoO/CoFe obtained in example 1 2 O 4 -1O 1s X ray photoelectron spectroscopy (XPS) of the electrode material.
FIG. 5 shows CoO/CoFe obtained in example 1 2 O 4 -1 electron paramagnetic resonance wave front (EPR) of the electrode material.
FIG. 6 shows CoO/CoFe obtained in example 2 2 O 4 -2 SEM pictures of the electrode material at different magnifications.
FIG. 7 shows CoO/CoFe obtained in example 2 2 O 4 -2 XRD pattern of electrode material.
FIG. 8 shows CoO/CoFe obtained in example 2 2 O 4 -2O 1s XPS plot of electrode material.
FIG. 9 shows CoO/CoFe obtained in example 3 2 O 4 -3 SEM pictures of the electrode material at different magnifications.
FIG. 10 shows CoO/CoFe obtained in example 3 2 O 4 -3 XRD pattern of electrode material.
FIG. 11 shows CoO/CoFe obtained in example 3 2 O 4 -3O 1s XPS plot of electrode material.
FIG. 12 is CoO/CoFe obtained in example 4 2 O 4 -4 SEM images of the electrode material at different magnifications.
FIG. 13 is CoO/CoFe obtained in example 4 2 O 4 -XRD pattern of 4 electrode materials.
FIG. 14 shows CoO/CoFe obtained in example 4 2 O 4 -O1 s XPS plot of 4 electrode materials.
Fig. 15 is a graph showing electrochemical performances of the electrode materials obtained in examples 1, 2, 3 and 4.
Detailed Description
In order to facilitate understanding of the invention, the invention will be further illustrated with reference to specific examples, which are provided for illustration only and do not limit the scope of the invention.
Example 1: coO/CoFe 2 O 4 Preparation of-1 and oxygen evolution Properties thereof
Dissolving cobalt nitrate (0.652g, 2.24mmol) and ferric nitrate (0.0646g, 0.16mmol) in 20mL of methanol (solution A), dissolving dimethylimidazole (0.262g, 3.2mmol) in 20mL of methanol (solution B), pouring the solution B into the solution A, uniformly mixing, and transferring the solution to a 50mL hydrothermal kettle; a pretreated 1X 4cm nickel foam substrate was added and the reaction was carried out at 120 ℃ for 2 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 several times, and performing vacuum overnight drying at 60 ℃ to obtain the CoFe-MOF.
Placing the foamed nickel loaded with the CoFe-MOF precursor in a porcelain boat, and placing the porcelain boat at a thermocouple in the middle section of a tubular furnace; 0.5g of NaBH is weighed 4 Placing in another porcelain boat, placing in the upstream of the tube furnace, heating to 350 deg.C at a speed of 2 deg.C/min under nitrogen atmosphere, and maintaining for 1 hr to obtain CoO/CoFe 2 O 4 -1 sample.
FIG. 1 is the CoO/CoFe obtained in example 1 2 O 4 -1 scanning electron microscope images of the material at different magnifications. The sample can be clearly seen to be a three-dimensional network porous structure built up from arrays of thicker nanosheets, with a sample thickness of about 0.51 μm.
FIG. 2 shows CoO/CoFe obtained in example 1 2 O 4 -1 transmission electron micrographs of the material at different magnifications. The ultrathin nanosheet structure can be clearly seen from the TEM image, and the lattice fringes on the graph in FIG. 2b can judge that the material is formed by CoO and CoFe 2 O 4 The composition, figure 2C results show that Co, fe, C, N, O elements are uniformly dispersed, wherein C, N is all from organic ligand 2-methylimidazole.
FIG. 3 shows CoO/CoFe obtained in example 1 2 O 4 -1X-ray diffraction pattern (XRD) of the material. As can be seen from the figure, coO/CoFe 2 O 4 The-1 sample contains cubic CoO (JCPDS No. 75-0418) and CoFe 2 O 4 (JCPDS No. 22-1086). The derived peaks at 2 θ values of 36.7 °, 42.6 °, 61.8 °, 74.1 °, and 78.0 ° correspond to the (111), (200), (220), (311), and (222) crystal planes of CoO, respectively. The derived peaks at 2 theta values of 35.4 deg., 56.9 deg. and 62.6 deg. correspond to CoFe 2 O 4 The (311), (511) and (440) crystal planes of (a) are in accordance with the TEM results of fig. 2.
FIG. 4 shows CoO/CoFe obtained in example 1 2 O 4 -1O 1s XPS plot of material. As can be seen from the figure, the produced CoO/CoFe 2 O 4 -1 oxygen vacancy concentration of the electrode material V o ＝30.02％。
FIG. 5 shows the electrode material CoO/CoFe 2 O 4 The EPR result of-1, with a clear signal at a g value of 2.0037, indicates that the material contains abundant oxygen vacancies. The deviation of the g value is probably due to the fact that the spin state of electrons changes, the conductivity and the charge distribution of the electrocatalyst can be adjusted, and the electrocatalytic performance of the OER is improved.
Example 2: coO/CoFe 2 O 4 Preparation of (E) -2 and oxygen evolution Properties thereof
Dissolving cobalt nitrate (0.652g, 2.24mmol) and ferric nitrate (0.0404g, 0.10mmol) in 20mL of methanol (solution A), dissolving dimethylimidazole (0.262g, 3.2mmol) in 20mL of methanol (solution B), pouring the solution B into the solution A, uniformly mixing, and transferring the solution to a 50mL hydrothermal kettle; a pretreated 1X 4cm nickel foam substrate was added and the reaction was carried out at 120 ℃ for 2 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 several times, and performing vacuum overnight drying at 60 ℃ to obtain the CoFe-MOF.
Placing the foamed nickel loaded with the CoFe-MOF precursor in a porcelain boat, and placing the porcelain boat at a thermocouple in the middle section of a tubular furnace; weighing 1.0g NaBH 4 Placing the ceramic boat in another ceramic boat, placing the ceramic boat at the upstream of the tube furnace, heating to 350 ℃ at the speed of 2 ℃/min in the argon atmosphere, and preserving the heat for 1 hour to obtain the CoO/CoFe 2 O 4 -2 samples.
FIG. 6 is the CoO/CoFe obtained in example 2 2 O 4 -2 SEM images of the material at different magnifications. The sample can be clearly seen to be a three-dimensional porous structure built up from arrays of nanoplatelets with smoother surfaces, and the sample thickness is approximately 0.49 μm.
FIG. 7 shows CoO/CoFe obtained in example 2 2 O 4 -2 XRD pattern of the material. As can be seen from the figure, sample CoFeO x N can be divided into cubic CoO (JCPDS No. 75-0418) and CoFe 2 O 4 (JCPDS no.22-1086)。
FIG. 8 shows CoO/CoFe obtained in example 2 2 O 4 -2O 1s XPS plot of material. As can be seen from the figure, the produced CoO/CoFe 2 O 4 -2 oxygen vacancy concentration of electrode material V o ＝26.08％。
Example 3: coO/CoFe 2 O 4 Preparation of (E) -3 and oxygen evolution Properties thereof
Dissolving cobalt nitrate (0.652g, 2.24mmol) and ferric nitrate (0.0565g, 0.14mmol) in 20mL of methanol (solution A), dissolving dimethylimidazole (0.262g, 3.2mmol) in 20mL of methanol (solution B), pouring the solution B into the solution A, uniformly mixing, and transferring the solution to a 50mL hydrothermal kettle; a pretreated 1X 4cm nickel foam matrix was added and reacted at 120 ℃ for 2 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 several times, and performing vacuum overnight drying at 60 ℃ to obtain the CoFe-MOF.
Placing the foamed nickel loaded with the CoFe-MOF precursor in a porcelain boat, and placing the porcelain boat at a thermocouple in the middle section of a tube furnace; 1.0g of NaBH is weighed 4 Placing in another porcelain boat, placing in the upstream of the tube furnace, heating to 350 deg.C at a rate of 2 deg.C/min in nitrogen atmosphere, and holding for 1 hr to obtain CoO/CoFe 2 O 4 -3 samples.
FIG. 9 is the CoO/CoFe obtained in example 3 2 O 4 -3 SEM pictures of the material at different magnifications. The sample can clearly be seen to be a three-dimensional porous structure built up from an array of nanoplates, with a sample thickness of approximately 0.46 μm.
FIG. 10 shows CoO/CoFe obtained in example 3 2 O 4 -3 materialsXRD pattern of (a). As can be seen from the figure, sample CoFeO x N can be divided into cubic CoO (JCPDS No. 75-0418) and CoFe 2 O 4 (JCPDS no.22-1086)。
FIG. 11 is the CoO/CoFe obtained in example 3 2 O 4 -3O 1s XPS plot of material. As can be seen from the figure, the produced CoO/CoFe 2 O 4 -3 oxygen vacancy concentration of electrode material V o ＝29.77％。
Example 4: coO/CoFe 2 O 4 Preparation of (E) -4 and oxygen evolution Properties thereof
Dissolving cobalt nitrate (0.652g, 2.24mmol) and ferric nitrate (0.0727g, 0.18mmol) in 20mL of methanol (solution A), dissolving dimethylimidazole (0.262g, 3.2mmol) in 20mL of methanol (solution B), pouring the solution B into the solution A, uniformly mixing, and transferring the solution to a 50mL hydrothermal kettle; a pretreated 1X 4cm nickel foam substrate was added and the reaction was carried out at 120 ℃ for 2 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 several times, and performing vacuum overnight drying at 60 ℃ to obtain the CoFe-MOF.
Placing the foamed nickel loaded with the CoFe-MOF precursor in a porcelain boat, and placing the porcelain boat at a thermocouple in the middle section of a tubular furnace; weighing 1g NaBH 4 Placing the ceramic boat in another ceramic boat, placing the ceramic boat at the upstream of the tube furnace, heating to 350 ℃ at the speed of 2 ℃/min in the argon atmosphere, and preserving the heat for 1 hour to obtain the CoO/CoFe 2 O 4 -4 samples.
FIG. 12 is the CoO/CoFe obtained in example 4 2 O 4 SEM images of 4 materials at different magnifications. The sample can be clearly seen to be a three-dimensional porous structure built up from an array of rough nanoplatelets, with a sample thickness of approximately 0.38 μm.
FIG. 13 is CoO/CoFe obtained in example 4 2 O 4 -XRD pattern of 4 materials. As can be seen from the figure, sample CoFeO x N can be divided into cubic CoO (JCPDS No. 75-0418) and CoFe 2 O 4 (JCPDS no.22-1086)。
FIG. 14 shows CoO/CoFe obtained in example 4 2 O 4 -O1 s XPS plot of 4 materials. From the figureAs can be seen, the CoO/CoFe produced 2 O 4 -4 oxygen vacancy concentration of electrode material V o ＝29.70％。
FIG. 15 shows the electrode material CoO/CoFe 2 O 4 Electrochemical performance diagram of 1/2/3/4 four electrode materials in 1M KOH solution:
as can be seen from the linear sweep voltammogram (LSV, FIG. 15 a), when the current density was 10 mA-cm -2 Of CoO/CoFe 2 O 4 Overpotential of-1 electrode 192mV vs CoO/CoFe 2 O 4 -2(295mV)，CoO/CoFe 2 O 4 -3 (218 mV) and CoO/CoFe 2 O 4 The overpotentials of-4 (277 mV) are all low, due to the different Fe doping levels and oxygen vacancy concentrations, coO/CoFe 2 O 4 -1 electrode having the highest concentration of oxygen vacancies (V) o = 30.02%), exposing more active sites. In addition, the overpotentials of these composite electrodes are much smaller than RuO 2 Catalytic electrode (360mV @10mA cm) -2 ) Indicating that it has the potential to replace noble metal catalysts.
As can be seen from the Tafel plot (FIG. 15 b), coO/CoFe 2 O 4 The slope of the Tafel curve of-1/2/3/4 is 42.53mV dec -1 ，60.53mV·dec -1 ，52.66mV·dec -1 ，59.95mV·dec -1 Description of CoO/CoFe 2 O 4 -1 has optimal OER reaction kinetics, and can accelerate the transmission rate of electrons, further illustrating that the electrode material of example 1 has optimal electrocatalytic oxygen evolution performance. Furthermore, with RuO 2 Electrode (126.70 mV dec -1 ) In contrast, all four composite electrodes have good catalytic kinetics.
The electrochemically effective active area (ECSA, FIG. 15 c) results indicate CoO/CoFe 2 O 4 The specific capacitance of the electric double layer of-1/2/3/4 four electrode materials is 48.77mF cm -2 ，22.79mF·cm -2 ，46.23mF·cm -2 ，36.08mF·cm -2 Description of CoO/CoFe 2 O 4 -1 has a larger electrochemically active area and can provide more OER active sites.
From the electrochemical impedance spectrum (EIS,FIG. 15 d) shows the correlation with CoO/CoFe 2 O 4 2 (1.68 and 18.51. Omega.), coO/CoFe 2 O 4 -3 (1.45 and 13.38 Ω) and CoO/CoFe 2 O 4 CoO/CoFe-4 (1.79 and 16.79. OMEGA.) 2 O 4 -1 had significantly smaller solution internal resistance (Rs) and charge transfer resistance (Rct) (1.24 and 8.45. OMEGA.), confirming CoO/CoFe 2 O 4 -1 the charge transfer kinetics at the electrode-electrolyte interface is faster and more favorable for faradaic processes, resulting in its excellent OER catalytic activity.
It can be seen from the above examples that the preparation method of the present invention is a relatively universal method, and the bimetallic MOFs precursor is obtained by simple hydrothermal treatment of a metal salt in a certain proportion, and then the oxygen vacancy is produced by a reduction calcination method, so as to obtain oxygen vacancy-rich CoO/CoFe 2 O 4 Composite materials, these samples all show better oxygen evolution performance in alkaline solution, wherein CoO/CoFe 2 O 4 -1 sample has optimal OER performance: the lowest oxygen evolution overpotential, the smallest tafel slope, the largest specific surface area of activity and the smallest resistance.
Claims (8)
1. Oxygen vacancy-rich CoO/CoFe 2 O 4 The catalyst with the nanosheet array structure is characterized by being prepared by the following method:
(1) Mixing a mixed solution of cobalt salt and ferric salt with an organic ligand solution, adding the mixed solution into a pretreated foamed nickel substrate, carrying out hydrothermal reaction for 1-6 h at 100-140 ℃, taking out the foamed nickel, and washing and drying to obtain a precursor material on the foamed nickel substrate;
the organic ligand is dimethyl imidazole, terephthalic acid or phthalic acid;
(2) Putting the foamed nickel loaded with the precursor material obtained in the step (1) into a tubular furnace, simultaneously putting reducing agent sodium borohydride powder, heating to 250-450 ℃ under the protection of inert gas, calcining for 0.5-4.5 h, and obtaining CoO/CoFe 2 O 4 A catalyst with a nano-sheet array structure.
2. Such asOxygen vacancy rich CoO/CoFe of claim 1 2 O 4 The nanosheet array structure catalyst is characterized in that in the step (1), in the mixed solution of the cobalt salt and the iron salt, the concentration of the cobalt salt is 100-120 mmol/L, and the molar ratio of the cobalt salt to the iron salt is 1: 0.04-0.08, and the solvent is methanol or acetone.
3. Oxygen vacancy rich CoO/CoFe as claimed in claim 1 2 O 4 The catalyst with the nanosheet array structure is characterized in that in the step (1), the concentration of the organic ligand solution is 100-400 mmol/L, and the solvent is methanol or acetone.
4. Oxygen vacancy rich CoO/CoFe as claimed in claim 1 2 O 4 The nanosheet array structure catalyst is characterized in that in the step (1), the volume ratio of the mixed solution of the cobalt salt and the ferric salt to the organic ligand solution is 1:1.
5. oxygen vacancy rich CoO/CoFe as claimed in claim 1 2 O 4 The nanosheet array structure catalyst is characterized in that in the step (1), the cobalt salt is selected from any one of cobalt nitrate, cobalt chloride and cobalt acetate.
6. Oxygen vacancy rich CoO/CoFe as claimed in claim 1 2 O 4 The catalyst with the nanosheet array structure is characterized in that in the step (1), the ferric salt is selected from any one of ferric chloride, ferric nitrate and ferric sulfate.
7. Oxygen vacancy rich CoO/CoFe as claimed in claim 1 2 O 4 The catalyst with the nanosheet array structure is characterized in that in the step (1), the foamed nickel substrate is pretreated before use as follows: sequentially cleaning the mixture by using acetone, deionized water, 3M hydrochloric acid, deionized water and absolute ethyl alcohol for 15 minutes under an ultrasonic condition, and drying the mixture in vacuum for later use.
8. Oxygen-rich vacancies as claimed in any of claims 1 to 7CoO/CoFe of 2 O 4 The application of the catalyst with the nano-sheet array structure in the electrolytic water oxygen evolution reaction.
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