A method for preparing a rare earth europium and oxygen vacancy defect co-doped cobalt tetroxide catalyst for electrocatalytic water decomposition to produce hydrogen

Abstract

The present invention provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen, the preparation method comprising the following steps: mixing a europium soluble salt, a cobalt soluble salt and a solvent, adding a precipitant thereto, and obtaining a mixed solution; subjecting the mixed solution to a solvothermal reaction and a calcination treatment in sequence to obtain europium-doped cobalt oxide; mixing the europium-doped cobalt oxide and a reducing agent, and after ultrasonication, obtaining a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects. The preparation method utilizes the synergistic effect between rare earth europium and oxygen vacancy defects, the addition of rare earth europium can optimize the redistribution of charge, the introduction of oxygen vacancy defects can generate impurity energy levels, and improve the electron transport capacity of the catalyst, thereby significantly improving the rate of the oxygen evolution reaction of the catalyst and reducing the energy barrier of the reaction; the obtained catalyst is environmentally friendly, non-toxic and harmless, and has excellent catalytic effect.

Description

Technical Field

[0001] The invention belongs to the field of electrocatalytic water decomposition to produce hydrogen, and in particular relates to a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Background Art

[0002] With the rapid development of economy and society, energy crisis and environmental pollution have become two major problems faced by the world. At present, fossil fuels (such as coal, oil, and natural gas) are still the main energy supply, but the reserves of these fossil fuels are limited, and they will release harmful substances and cause environmental pollution during the combustion process. Therefore, it is of great significance to develop clean and sustainable energy carriers that can replace traditional fossil fuels.

[0003] As a clean energy with high energy density and no carbon emissions, hydrogen has always been considered an important product to replace carbon-based energy in the future. Electrocatalytic water decomposition to produce hydrogen technology is an environmentally friendly and efficient hydrogen production pathway, which includes two half reactions, namely the oxygen evolution reaction on the anode and the hydrogen evolution reaction on the cathode. The oxygen evolution reaction is a complex reaction involving an electron transfer process. It has a high reaction energy barrier and a slow reaction rate, which has become a "bottleneck" for water decomposition to produce hydrogen. Therefore, it is of great significance to prepare an efficient, stable and low-cost oxygen evolution reaction catalyst, accelerate the rate of water decomposition to produce hydrogen, and reduce the energy barrier for hydrogen production.

[0004] Currently, the most useful catalysts for oxygen evolution reaction are nanomaterials based on precious metals Ir and Ru. However, the reserves of precious metals are low and the cost is high, which limits their large-scale application. Cobalt tetroxide materials have attracted the research interest of a wide range of scholars due to their simple preparation, low cost and outstanding catalytic effect. However, cobalt tetroxide-based catalysts also face two problems: (1) poor electrical conductivity. Due to the large band gap, the electron transport capacity of cobalt tetroxide is insufficient, which affects the charge transfer during the reaction; (2) inappropriate adsorption capacity for oxygen species (H2O, OH, O, OOH, O2). Due to the large difference between its own electronic structure and that of precious metals, the adsorption energy of cobalt tetroxide for some oxygen species is too strong or too weak, which is not conducive to the adsorption and activation of reactants and the transfer and desorption of products, resulting in a high energy barrier for the reaction.

[0005] CN109576730A discloses a preparation method and application of an iron-modified cobalt tetroxide nanosheet array electrode, the preparation method comprising: 1. treating carbon cloth; 2. preparing solution; 3. soaking; 4. anion etching; 5. annealing treatment to obtain a cobalt tetroxide nanosheet array electrode and an iron-modified cobalt tetroxide nanosheet array electrode. The iron modification method is used to improve the conductivity of the catalyst and increase the number of sites of the catalyst, thereby improving its performance in catalyzing oxygen evolution reaction.

[0006] CN110479274A discloses a method for preparing Co3O4-CuCoO2 nano-mesh material by aluminum powder sacrificial method, using copper nitrate, cobalt nitrate, potassium hydroxide and aluminum powder as raw materials, and then subjecting them to hydrothermal reaction at 200°C for 20 hours, cooling to room temperature, centrifuging and washing with water, and vacuum drying at 60°C to obtain Co3O4-CuCoO2 nano-mesh. The preparation method improves the performance of catalytic oxygen evolution reaction by optimizing the adsorption and desorption process of intermediate products.

[0007] The preparation method of the above catalyst is relatively complicated and can only alleviate some of the problems of oxide catalysts. Therefore, it is urgent to develop a cobalt tetroxide-based catalyst with a simple preparation method and which can simultaneously improve the conductivity and adsorption capacity of cobalt tetroxide. Summary of the invention

[0008] The object of the present invention is to provide a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. The preparation method is simple to operate, rapid to synthesize, and has good universality. The prepared catalyst can realize catalytic oxygen evolution reaction, accelerate the reaction rate, and reduce the reaction energy barrier.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. The preparation method comprises the following steps:

[0011] (1) mixing a europium soluble salt, a cobalt soluble salt and a solvent, and adding a precipitant thereto to obtain a mixed solution;

[0012] (2) subjecting the mixed solution of step (1) to a solvothermal reaction and a calcination treatment in sequence to obtain europium-doped cobalt tetroxide;

[0013] (3) Mixing the europium-doped cobalt tetroxide described in step (2) with a reducing agent, and subjecting the mixture to ultrasonic treatment to obtain a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects.

[0014] In the preparation method of the present invention, during the solvent thermal process, the precipitant provides an alkaline environment so that the cobalt ions (Co 3+ ) and europium ions (Eu 3+) co-precipitate to form a Eu-doped cobalt hydroxide precursor, which is then calcined to obtain europium-doped cobalt tetroxide. Since europium is rich in extranuclear electrons, its introduction can induce the redistribution of the charge of cobalt oxide; europium-doped cobalt tetroxide is mixed with a reducing agent, and the reducing agent can compete with the oxygen atoms on the surface of the oxide to form a certain concentration of oxygen vacancy defects, which can reduce the band gap width of cobalt oxide and introduce impurity energy levels into the band gap, which is beneficial to improving the conductivity of cobalt oxide.

[0015] The present invention utilizes the synergistic regulatory effect of rare earth Eu and oxygen vacancy defects on the electronic structure of cobalt tetroxide. On the one hand, it induces the redistribution of surface charge of cobalt oxide, and on the other hand, it utilizes the regulation of the energy band structure of cobalt oxide to optimize the adsorption / desorption ability of oxygen species and reduce the energy barrier of the reaction; it improves the electrical conductivity, promotes charge transfer during the reaction, and accelerates the reaction rate.

[0016] As a preferred technical solution of the present invention, the molar ratio of the europium soluble salt to the cobalt soluble salt in step (1) is 1:(4-20), for example, it can be 1:4, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18 or 1:20, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 1:(6-10).

[0017] Preferably, the europium soluble salt in step (1) comprises europium nitrate.

[0018] Preferably, the cobalt soluble salt in step (1) comprises cobalt nitrate.

[0019] As a preferred technical solution of the present invention, the volume ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the solvent in step (1) is 1:(30-40) mol / L, for example, it can be 1:30 mol / L, 1:32 mol / L, 1:34 mol / L, 1:36 mol / L, 1:38 mol / L or 1:40 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the solvent in step (1) is a mixed solution of water and ethanol.

[0021] Preferably, the volume ratio of water to ethanol is 1:(0.5-1.5), for example, it can be 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.1, 1:1.3 or 1:1.5, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] As a preferred technical solution of the present invention, the molar ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the precipitant in step (1) is 1:(5-7), for example, it can be 1:5, 1:5.4, 1:5.8, 1:6, 1:6.4, 1:6.8 or 1:7, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the precipitant in step (1) comprises urea.

[0024] As a preferred technical solution of the present invention, the temperature of the solvent thermal reaction in step (2) is 80-120°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the solvent thermal reaction time in step (2) is 8-12 h, for example, it can be 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h or 12 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] As a preferred technical solution of the present invention, the solvent thermal reaction and calcination treatment in step (2) also include solid-liquid separation, washing and drying performed sequentially.

[0027] As a preferred technical solution of the present invention, the calcination treatment in step (2) is carried out in an air atmosphere.

[0028] Preferably, the temperature of the calcination treatment in step (2) is 350-450°C, for example, 350°C, 370°C, 390°C, 400°C, 430°C or 450°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the calcination time in step (2) is 1-3 h, for example, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h or 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, the mass ratio of the europium-doped cobalt tetroxide and the reducing agent in step (3) is 2:(1-3), for example, it can be 2:1, 2:2.4, 2:2.8, 2:2, 2:2.4, 2:2.8 or 2:3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the concentration of the reducing agent in step (3) is 0.5-2.0 mg / mL, for example, 0.5 mg / mL, 1.0 mg / mL, 1.5 mg / mL or 2.0 mg / mL, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 0.8-1.2 mg / mL.

[0032] Preferably, the reducing agent in step (3) comprises an aqueous solution of potassium borohydride.

[0033] As a preferred technical solution of the present invention, the ultrasonic time in step (3) is 0.5-1.5h, for example, it can be 0.5h, 0.7h, 0.9h, 1h, 1.1h, 1.3h or 1.5h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the step (3) further comprises solid-liquid separation, washing and drying after the ultrasonic treatment.

[0035] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0036] (1) mixing a europium soluble salt, a cobalt soluble salt and a solvent, and adding a precipitant thereto to obtain a mixed solution;

[0037] The molar ratio of the europium soluble salt to the cobalt soluble salt is 1:(4-20); the volume ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the solvent is 1:(30-40) mol / L; the molar ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the precipitant is 1:(5-7);

[0038] (2) subjecting the mixed solution of step (1) to a solvothermal reaction at 80-120° C. for 8-12 h, and after solid-liquid separation, washing and drying, calcining at 300-400° C. in an air atmosphere for 1-3 h to obtain europium-doped cobalt tetroxide;

[0039] (3) The europium-doped cobalt tetroxide described in step (2) and a reducing agent having a concentration of 0.5-2.0 mg / mL are mixed in a mass ratio of 2:(1-3), and after ultrasonic treatment for 0.5-1.5 h, solid-liquid separation, washing and drying, a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects is obtained.

[0040] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The preparation method of the present invention utilizes the synergistic effect between rare earth Eu and oxygen vacancy defects. The addition of rare earth Eu can optimize the redistribution of charge, and the introduction of oxygen vacancy defects can enhance the electron transport capacity of the catalyst, thereby significantly improving the rate of the oxygen evolution reaction of the catalyst and reducing the energy barrier of the reaction; the prepared catalyst is environmentally friendly, non-toxic and harmless, and has excellent catalytic effect;

[0043] (2) The preparation method of the present invention is simple, easy to operate, and has universal applicability. It can prepare different types of rare earth-doped oxide materials and introduce different concentrations of oxygen vacancy defects, thereby providing guidance for the preparation of rare earth and vacancy defect co-doped oxide catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The oxygen evolution reaction performance curves of the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0045] Figure 2 XRD spectra of the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention;

[0046] Figure 3 BET spectra of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen, the preparation method comprising the following steps:

[0050] (1) 0.2 mmol Eu(NO3)3·6H2O and 1.8 mmol Co(NO3)3·6H2O were added to a mixed solution of 35 mL deionized water and 35 mL ethanol, and 720 mg urea was added thereto after stirring to obtain a mixed solution;

[0051] (2) subjecting the mixed solution of step (1) to a solvothermal reaction at 100° C. for 10 h, filtering, washing and drying, and then calcining in air at 350° C. for 2 h to obtain europium-doped cobalt tetroxide;

[0052] (3) The europium-doped cobalt tetroxide described in step (2) and a 1.0 mg / mL potassium borohydride aqueous solution are mixed in a mass ratio of 2:2, and after ultrasonic treatment for 1 h, suction filtration, washing and drying at 60° C., an oxygen vacancy europium-doped cobalt tetroxide catalyst is obtained.

[0053] Example 2

[0054] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen, the preparation method comprising the following steps:

[0055] (1) 0.25 mmol Eu(NO3)3·6H2O and 1.75 mmol Co(NO3)3·6H2O were added to a mixed solution of 35 mL deionized water and 35 mL ethanol, and 750 mg urea was added thereto after stirring to obtain a mixed solution;

[0056] (2) subjecting the mixed solution of step (1) to a solvothermal reaction at 90° C. for 12 h, filtering, washing and drying, and then calcining in air at 300° C. for 3 h to obtain europium-doped cobalt tetroxide;

[0057] (3) The europium-doped cobalt tetroxide described in step (2) and a 2.0 mg / mL potassium borohydride aqueous solution are mixed in a mass ratio of 2:1, and after ultrasonic treatment for 0.5 h, filtration, washing and drying at 60° C., an oxygen vacancy europium-doped cobalt tetroxide catalyst is obtained.

[0058] Example 3

[0059] The present embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that step (1) "0.2mmol Eu(NO3)3·6H2O and 1.8mmol Co(NO3)3·6H2O" is replaced by "0.1mmol Eu(NO3)3·6H2O and 1.9mmol Co(NO3)3·6H2O", other conditions are the same as those in Example 1.

[0060] Example 4

[0061] The present embodiment provides a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that step (1) "0.2mmol Eu(NO3)3·6H2O and 1.8mmol Co(NO3)3·6H2O" is replaced by "0.3mmol Eu(NO3)3·6H2O and 1.7mmol Co(NO3)3·6H2O", other conditions are the same as those in Example 1.

[0062] Example 5

[0063] The present embodiment provides a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that step (1) "0.2mmol Eu(NO3)3·6H2O and 1.8mmol Co(NO3)3·6H2O" is replaced by "0.4mmol Eu(NO3)3·6H2O and 1.6mmol Co(NO3)3·6H2O", other conditions are the same as those in Example 1.

[0064] Example 6

[0065] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the calcination temperature in step (2) is 300°C, other conditions are the same as those in Example 1.

[0066] Example 7

[0067] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the calcination temperature in step (2) is 500° C., other conditions are the same as those in Example 1.

[0068] Example 8

[0069] This embodiment provides a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the mass ratio of europium-doped cobalt tetroxide to potassium borohydride aqueous solution in step (3) is 2:0.6, other conditions are the same as those in Example 1.

[0070] Example 9

[0071] This embodiment provides a method for preparing a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the mass ratio of europium-doped cobalt tetroxide to potassium borohydride aqueous solution in step (3) is 2:4, other conditions are the same as those in Example 1.

[0072] Example 10

[0073] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the concentration of the potassium borohydride aqueous solution in step (3) is 0.5 mg / mL, other conditions are the same as those in Example 1.

[0074] Embodiment 11

[0075] This embodiment provides a method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen. Except that the concentration of the potassium borohydride aqueous solution in step (3) is 1.5 mg / mL, other conditions are the same as those in Example 1.

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a cobalt tetroxide catalyst. Except that step (1) "0.2mmol Eu(NO3)3·6H2O and 1.8mmol Co(NO3)3·6H2O" is replaced by "2mmol Co(NO3)3·6H2O" and step (3) is not performed, other conditions are the same as those in Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing an oxygen vacancy defect cobalt tetroxide catalyst, except that the step (1) "0.2mmol Eu(NO3)3·6H2O and 1.8mmol Co(NO3)3·6H2O" is replaced by "2mmol Co(NO3)3·6H2O", the other conditions are the same as those in Example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing a rare earth europium-doped cobalt tetroxide catalyst. Except that step (3) is not performed, other conditions are the same as those in Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a method for preparing a cobalt tetroxide catalyst co-doped with rare earth lanthanum and oxygen vacancy defects. Except that the "0.2 mmol Eu(NO3)3·6H2O" in step (1) is replaced by "0.2 mmol La(NO3)2·6H2O", other conditions are the same as those in Example 1.

[0084] Comparative Example 5

[0085] This comparative example provides a method for preparing a cobalt oxide catalyst co-doped with rare earth cerium and oxygen vacancy defects. Except that the "0.2mmol Eu(NO3)3·6H2O" in step (1) is replaced by "0.2mmol Ce(NO3)3·6H2O", other conditions are the same as those in Example 1.

[0086] The catalysts prepared in the above examples and comparative examples were subjected to oxygen evolution reaction tests, specifically: in a standard three-electrode electrolytic cell, 1.0 M potassium hydroxide solution was used as the electrolyte, the prepared catalyst was coated on a glassy carbon electrode as the working electrode, and the catalytic oxygen evolution reaction was detected to reach 10 mA cm -2 The overpotential at , the specific results are shown in Table 1. Among them, the oxygen evolution reaction performance curves of the catalysts prepared in Example 1 and Comparative Examples 1-3 are shown in Figure 1 shown.

[0087] Table 1

[0088]

[0089]

[0090] From Table 1, we can draw the following conclusions:

[0091] (1) The preparation method provided in Example 1 of the present invention is used to prepare a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects, which has excellent catalytic performance through the synergistic regulation of the electronic structure of cobalt oxide by rare earth Eu and oxygen vacancy defects;

[0092] (2) It can be seen from Example 1 and Examples 3-5 that when the Eu doping in the cobalt tetroxide catalyst is too low, the degree of charge redistribution in the cobalt tetroxide is relatively small, resulting in a decrease in the catalytic performance of the catalyst; when the Eu doping in the cobalt tetroxide catalyst is too high, the degree of charge redistribution in the cobalt tetroxide is high, and the adsorption capacity for intermediate species is too weak, resulting in a decrease in the catalytic performance of the catalyst;

[0093] (3) It can be seen from Example 1 and Examples 8-9 that when the amount of reducing agent added is too little, the number of oxygen vacancy defects generated is too small, and the synergistic effect between rare earth Eu and oxygen vacancy defects is weak, resulting in low catalytic performance of the catalyst; when the amount of reducing agent added is too much, although it does not affect the catalytic performance of the catalyst, it increases the production cost; It can be seen from Example 1 and Examples 10-11 that when the concentration of the reducing agent is too low or too high, it will cause uneven distribution of oxygen vacancy defects, resulting in decreased catalytic performance of the catalyst;

[0094] (4) Based on Example 1 and Comparative Examples 2 and 3, it can be seen that when the catalyst is not doped with Eu or has no oxygen vacancy defects, the synergistic effect between rare earth Eu and oxygen vacancy defects cannot occur, resulting in a decrease in the catalytic performance of the catalyst;

[0095] (5) Based on Example 1 and Comparative Examples 4-5, it can be seen that when other rare earth elements are doped, the synergistic effect between them and oxygen vacancy defects is greatly reduced, resulting in a decrease in the catalytic performance of the catalyst.

[0096] The catalysts prepared in Example 1 and Comparative Examples 1-3 were characterized by XRD and BET. The characterization results are as follows: Figure 2-3 As shown in the figure, after co-doping with oxygen vacancies and rare earth Eu, the crystal structure of the catalyst still maintains the cubic phase of cobalt tetroxide, which is highly consistent with the standard card (PDF: 43-1003); the morphology of the catalyst has not changed much, and it is still in the form of nanorods; the specific surface area of ​​the catalyst has changed slightly. It further shows that the improvement of the oxygen evolution reaction performance of the prepared catalyst is mainly attributed to the synergistic regulation of oxygen vacancies and rare earth Eu on the electronic structure of cobalt tetroxide, rather than the change of crystal form, morphology and specific surface area.

[0097] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a cobalt oxide catalyst co-doped with rare earth europium and oxygen vacancy defects for electrocatalytic water decomposition to produce hydrogen, characterized in that: The preparation method comprises the following steps: (1) mixing a europium soluble salt, a cobalt soluble salt and a solvent, and adding a precipitant thereto to obtain a mixed solution; (2) subjecting the mixed solution of step (1) to a solvothermal reaction and a calcination treatment in sequence to obtain europium-doped cobalt tetroxide; (3) Mixing the europium-doped cobalt tetroxide described in step (2) with a reducing agent, and subjecting the mixture to ultrasonic treatment to obtain a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the europium soluble salt to the cobalt soluble salt in step (1) is 1:(4-20).

3. The preparation method according to claim 2, characterized in that: The molar ratio of the europium soluble salt to the cobalt soluble salt in step (1) is 1:(6-10).

4. The preparation method according to claim 1, characterized in that: The europium soluble salt in step (1) includes europium nitrate.

5. The preparation method according to claim 1, characterized in that: The cobalt soluble salt in step (1) comprises cobalt nitrate.

6. The preparation method according to claim 1, characterized in that: The volume ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the solvent in step (1) is 1:(30-40) mol / L.

7. The preparation method according to claim 1, characterized in that: The solvent in step (1) is a mixed solution of water and ethanol.

8. The preparation method according to claim 7, characterized in that: The volume ratio of water to ethanol is 1:(0.5-1.5).

9. The preparation method according to claim 1, characterized in that: The molar ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the precipitant in step (1) is 1:(5-7).

10. The preparation method according to claim 1, characterized in that: The precipitant in step (1) comprises urea.

11. The preparation method according to claim 1, characterized in that: The temperature of the solvent thermal reaction in step (2) is 80-120°C.

12. The preparation method according to claim 1, characterized in that: The solvent thermal reaction time of step (2) is 8-12h.

13. The preparation method according to claim 1, characterized in that: The solvent thermal reaction and calcination treatment in step (2) also include solid-liquid separation, washing and drying performed in sequence.

14. The preparation method according to claim 1, characterized in that: The calcination treatment in step (2) is carried out in an air atmosphere.

15. The preparation method according to claim 1, characterized in that: The temperature of the calcination treatment in step (2) is 350-450°C.

16. The preparation method according to claim 1, characterized in that: The calcination time in step (2) is 1-3 hours.

17. The preparation method according to claim 1, characterized in that: The mass ratio of the europium-doped cobalt tetroxide to the reducing agent in step (3) is 2:(1-3).

18. The preparation method according to claim 1, characterized in that: The concentration of the reducing agent in step (3) is 0.5-2.0 mg / mL.

19. The preparation method according to claim 18, characterized in that: The concentration of the reducing agent in step (3) is 0.8-1.2 mg / mL.

20. The preparation method according to claim 1, characterized in that: The reducing agent in step (3) includes an aqueous solution of potassium borohydride.

21. The preparation method according to claim 1, characterized in that: The ultrasonic time in step (3) is 0.5-1.5h.

22. The preparation method according to claim 1, characterized in that: After the ultrasound in step (3), the process also includes solid-liquid separation, washing and drying.

23. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (1) mixing a europium soluble salt, a cobalt soluble salt and a solvent, and adding a precipitant thereto to obtain a mixed solution; The molar ratio of the europium soluble salt to the cobalt soluble salt is 1:(4-20); the volume ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the solvent is 1:(30-40) mol / L; the molar ratio of the total molar amount of the europium soluble salt and the cobalt soluble salt to the precipitant is 1:(5-7); (2) subjecting the mixed solution of step (1) to a solvothermal reaction at 80-120° C. for 8-12 h, and after solid-liquid separation, washing and drying, calcining at 300-400° C. in an air atmosphere for 1-3 h to obtain europium-doped cobalt tetroxide; (3) The europium-doped cobalt tetroxide described in step (2) and a reducing agent having a concentration of 0.5-2.0 mg / mL are mixed in a mass ratio of 2:(1-3), and after ultrasonic treatment for 0.5-1.5 h, solid-liquid separation, washing and drying, a cobalt tetroxide catalyst co-doped with rare earth europium and oxygen vacancy defects is obtained.

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