Cobalt diselenide / reduced graphene oxide electrocatalyst and preparation method thereof

Abstract

The invention belongs to the technical field of electrocatalytic oxygen evolution reaction, and particularly relates to a method for preparing a cobalt diselenide reduced graphene oxide electrocatalyst by taking ZIF-67 as a precursor. The invention solves the problems of poor conductivity and easy agglomeration of cobalt diselenide, and develops an electro-catalytic oxygen evolution reaction catalyst with low cost and high catalytic performance. The electrocatalyst provided by the invention adopts foamed nickel to bear cobalt diselenide and graphene oxide. The preparation method comprises the following steps: step 1, mixing a 2-methylimidazole solution with a cobalt nitrate hexahydrate solution to obtain a ZIF-67 precursor; 2, the foamed nickel is sequentially cleaned with ethyl alcohol and deionized water in an ultrasonic cleaner and then dried; and 3, dispersing the ZIF-67 precursor in water, adding graphene oxide, sodium hydroxide, ethylenediamine tetraacetic acid, sodium borohydride and sodium selenite into the solution, mixing, carrying out a hydrothermal reaction with foamed nickel, washing the product after the reaction, and drying.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic oxygen evolution reaction, and particularly relates to a method for preparing cobalt diselenide-reduced graphene oxide electrocatalyst with ZIF-67 as a precursor. Background Art

[0002] The combustion and use of fossil fuels have led to the emission of many greenhouse gases and other harmful substances into the atmosphere. Using other clean energy sources to replace fossil fuels is an effective way to solve this problem. Among them, hydrogen has attracted extensive attention in the energy field due to its high calorific value, high energy density, and only water as the combustion product. Electrocatalytic water splitting provides an effective means to solve the energy crisis and develop hydrogen energy. Performance-excellent electrocatalysts generally originate from precious metals, but they have problems such as high price and scarce reserves. Therefore, it is urgent to develop non-precious metal-based electrocatalysts with wide sources, high cost performance, and excellent performance.

[0003] Cobalt diselenide has advantages such as high catalytic activity and good stability, and has received extensive attention in the field of electrocatalytic oxygen evolution reaction. However, due to its disadvantages such as poor conductivity and easy agglomeration, its application in electrocatalytic oxygen evolution reaction is limited. At the same time, in the prior art, there are few reports on the synthesis of cobalt diselenide electrocatalyst by hydrothermal method, and there is still much room for improvement in aspects such as synthesis methods and design strategies.

[0004] Therefore, it is necessary to develop a low-cost and efficient method to solve the above problems. Adding functional carbon materials during the synthesis of the catalyst to achieve in-situ composite of cobalt diselenide and functional carbon materials can not only enhance the conductivity of the electrocatalyst, but also avoid the coverage of active sites caused by the agglomeration of cobalt diselenide, thereby improving the electrocatalytic oxygen evolution performance of the catalyst. In addition, using Co-MOF as a precursor to improve the structure of the final cobalt diselenide, making it more conducive to promoting the oxygen evolution reaction, can further improve the performance of the electrocatalyst. The combination of the above two improvement methods by hydrothermal synthesis in the present invention is an effective method for preparing low-cost and high-performance electrocatalysts. Summary of the Invention

[0005] The purpose of the present invention is to provide a cobalt diselenide / reduced graphene oxide electrocatalyst supported on nickel foam prepared with ZIF-67 as a precursor and its preparation method, to solve the problems of poor conductivity and easy agglomeration of cobalt diselenide, and to develop a low-cost and high-catalytic-performance electrocatalytic oxygen evolution reaction catalyst.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The cobalt diselenide / reduced graphene oxide electrocatalyst of the present invention is characterized in that nickel foam is used to carry cobalt diselenide and graphene oxide.

[0008] As a preferred embodiment, the mass ratio of cobalt diselenide to graphene oxide in the present invention is: 1: 0.1 to 0.8.

[0009] As another preferred embodiment, the mass ratio of cobalt diselenide to graphene oxide in the present invention is: 1: 0.28 or 1: 0.46 or 1: 0.65.

[0010] The preparation method of the cobalt diselenide / reduced graphene oxide electrocatalyst of the present invention comprises the following steps:

[0011] Step 1: Mix a 2-methylimidazole solution with a cobalt nitrate hexahydrate solution, stir, cool to room temperature after the reaction, and subject the obtained product to centrifugation, washing, and drying in sequence to obtain a ZIF-67 precursor;

[0012] Step 2: Clean nickel foam with alcohol and deionized water in a ultrasonic cleaner in sequence and then dry it to obtain pretreated nickel foam;

[0013] Step 3: Disperse the ZIF-67 precursor in water, add graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite to the solution and mix them. Then, put the mixed solution and nickel foam into a hydrothermal reaction kettle for hydrothermal reaction. Wash the product after the reaction with deionized water and ethanol in sequence and then dry it to obtain the electrocatalyst.

[0014] As a preferred embodiment, in Step 1 of the present invention: Mix a 2-methylimidazole solution with a cobalt nitrate hexahydrate solution, perform constant-temperature mechanical stirring or magnetic stirring under the condition of 0 to 100 °C, the rotor speed is 500 r / min to 1000 r / min, and cool to room temperature after reacting for 24 h to 72 h;

[0015] Both the centrifugation and washing are carried out using a centrifuge. In the centrifugation process, directly load the solution after the reaction into a centrifuge tube and then put it into the centrifuge for centrifugation; the washing process is to add deionized water or ethanol to the powder obtained after centrifugation and centrifuge again to remove the remaining impurities; the centrifuge speed in the centrifugation and washing processes is 4000 rpm to 8000 rpm, the centrifugation time is 3 min to 7 min; the number of washing times is 2 to 4 times;

[0016] The drying temperature is 5 °C to 100 °C, and the drying time is 8 h to 72 h.

[0017] As another preferred embodiment, in Step 1 of the present invention, the concentration of the 2-methylimidazole solution is 0.01 mol / L to 1 mol / L, and the concentration of the cobalt nitrate hexahydrate solution is 0.01 mol / L to 1 mol / L.

[0018] As another preferred embodiment, in step 1 of the present invention, the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1:0.1 to 1.0.

[0019] As another preferred embodiment, step 2 of the present invention: Cut the nickel foam into 3 cm 2 to 9 cm 2 and then put it into the first container filled with alcohol, and put the first container into an ultrasonic cleaner for cleaning for 5 min to 30 min; Take out the nickel foam in the first container and put it into the second container filled with deionized water, and put the second container into an ultrasonic cleaner for cleaning for 5 min to 30 min; Then dry for 8 h to 72 h to obtain the pretreated nickel foam.

[0020] The nickel foam is in the form of a thin sheet, and the nickel foam is cut into 3 cm 2 to 9 cm 2 which not only avoids damage to the nickel foam caused by high temperature during the reaction process, but also avoids too large nickel foam sheets resulting in too little material loading per unit area and reduced performance.

[0021] Clean with alcohol first and then with deionized water. Alcohol can wash away the oil stains, organic substances, etc. on the surface of the nickel foam during production or transportation, and deionized water can wash away the dust and particles on the surface of the nickel foam.

[0022] As another preferred embodiment, in step 3 of the present invention, the concentration of the dispersion of the ZIF-67 precursor in water is 0.01 mol / L to 0.10 mol / L.

[0023] As another preferred embodiment, in step 3 of the present invention, the product after the reaction is first rinsed with deionized water and then with ethanol; Repeat 2 to 4 times; Then dry.

[0024] Repeated rinsing multiple times can ensure the cleanliness of the cleaning and avoid residual impurities.

[0025] As another preferred embodiment, in step 3 of the present invention, the mass ratio of the ZIF-67 precursor to graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride and sodium selenite is 1:0.1 to 5.0:0.1 to 5.0:0.1 to 5.0:0.1 to 5.0:0.1 to 5.0.

[0026] Secondly, in step 3 of the present invention, the hydrothermal reaction process is as follows: At 150 °C to 210 °C, after hydrothermal reaction for 12 hours to 48 hours, cool to room temperature.

[0027] In addition, the mass concentration of the ethanol solution in the present invention is 99.5%.

[0028] Advantages of the present invention.

[0029] The present invention uses a hydrothermal method to prepare a cobalt diselenide / reduced graphene oxide electrocatalyst supported on nickel foam with ZIF-67 as the precursor. Compared with the two methods separately used in the background technology, the present invention greatly improves the oxygen evolution performance of the prepared electrocatalyst. The present invention also adds nickel foam during the preparation of the catalyst, and loads the final catalyst on nickel foam to ensure that the final product is a whole macroscopic sheet structure. Compared with the powder catalyst, the catalyst of the present invention does not require the addition of an additional binder during use, avoiding the increase of additional resistance and further improving the performance. At the same time, the hydrothermal method used in the present invention has a simple synthesis process, low cost and does not cause environmental pollution, and can be widely applied to industrial production.

[0030] Under the process parameter conditions of the present invention, it can ensure the smooth synthesis of ZIF-67, and successfully prepare a cobalt diselenide / reduced graphene oxide electrocatalyst supported on nickel foam by using the hydrothermal method with it as the precursor.

[0031] In the present invention, reduced graphene oxide and cobalt diselenide are supported on nickel foam. While enhancing the conductivity of the electrocatalyst, reduced graphene oxide can also disperse cobalt diselenide, avoiding the coverage of active sites caused by the aggregation of cobalt diselenide, thereby improving the oxygen evolution performance of the catalyst.

[0032] The present invention prepares an electrocatalytic oxygen evolution reaction catalyst, which has the characteristics of high catalytic activity and high stability, can effectively promote the electrocatalytic oxygen evolution reaction, has excellent performance in the electrocatalytic oxygen evolution reaction, and can be applied to the oxygen evolution reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The following further describes the present invention in conjunction with the drawings and specific embodiments. The protection scope of the present invention is not limited to the description of the following content.

[0034] Figure 1 It is a scanning electron microscope image of the electrocatalyst prepared in Example 1.

[0035] Figure 2 It is a scanning electron microscope image of the electrocatalyst prepared in Comparative Example 1.

[0036] Figure 3 It is a scanning electron microscope image of the electrocatalyst prepared in Comparative Example 2.

[0037] Figure 4 It is a comparison chart of the oxygen evolution curves of the electrocatalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2.

[0038] Figure 5 It is the stability performance diagram of the electrocatalyst prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited by the embodiments.

[0040] Example 1

[0041] Step 1: Stir 2-methylimidazole thoroughly and dissolve it completely in deionized water to obtain solution A; stir cobalt nitrate hexahydrate thoroughly and dissolve it completely in deionized water to obtain solution B; the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1:0.89, and the volume of deionized water is 4 times the total mass.

[0042] Slowly pour solution A into solution B to obtain solution C.

[0043] After reacting solution C at 25 °C for 48 hours, centrifuge, wash, and dry solution C to obtain a ZIF-67 precursor.

[0044] Step 2: Cut the nickel foam into a rectangle of 3 cm × 1.5 cm, put it into the first beaker containing 50 ml of alcohol, and then place the first beaker in an ultrasonic cleaner for 10 minutes; take out the nickel foam in the first beaker and put it into the second beaker containing 50 ml of deionized water, and then place the second beaker in an ultrasonic cleaner for 10 minutes; put the washed nickel foam into an oven and dry it at 60 °C for 12 hours to obtain the pretreated nickel foam.

[0045] Step 3: Add the ZIF-67 precursor, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite to deionized water, stir thoroughly until completely dissolved to obtain solution D, and the mass ratio of ZIF-67, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite is 1:0.46:4.3:4.3:0.21:1.5.

[0046] After adding solution D and the pretreated nickel foam into a hydrothermal reaction kettle, place the hydrothermal reaction kettle in an oven and react at a constant temperature of 180 °C for 12 hours, then cool it to room temperature in the air. Rinse the obtained solid with ethanol and deionized water 3 times (rinsing can be carried out using a wash bottle), put it into an oven, and dry it at 60 °C for 12 hours to obtain an electrocatalyst prepared with ZIF-67 as the precursor; the mass ratio of cobalt diselenide to graphene oxide in the electrocatalyst is: 1:0.46.

[0047] Figure 1 The figure is the scanning electron microscope image of the electrocatalyst prepared with ZIF-67 as the precursor. It can be seen from the figure that the presence of graphene oxide makes cobalt diselenide disperse evenly instead of agglomerating, and ZIF- sixty-seven as the precursor makes the prepared electrocatalyst have a spherical structure, which is beneficial to promoting the oxygen evolution reaction.

[0048] Example 2

[0049] Step 1: Stir 2-methylimidazole thoroughly and dissolve it completely in deionized water to obtain solution A; stir cobalt nitrate hexahydrate thoroughly and dissolve it completely in deionized water to obtain solution B; the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1:0.89, and the volume of deionized water is 4 times the total mass (the total mass refers to the weight of 2-methylimidazole plus cobalt nitrate hexahydrate);

[0050] Slowly pour solution A into solution B to obtain solution C;

[0051] After reacting solution C at 25 °C for 48 hours, centrifuge, wash, and dry solution C to obtain the ZIF-67 precursor;

[0052] Step 2: Cut the nickel foam into a rectangle of 3 cm × 1.5 cm, put it into the first beaker containing 50 ml of alcohol, and then place the first beaker in an ultrasonic cleaner for 10 minutes; take out the nickel foam in the first beaker and put it into the second beaker containing 50 ml of deionized water, and then place the second beaker in an ultrasonic cleaner for 10 minutes; put the washed nickel foam into an oven and dry it at 60 °C for 12 hours to obtain the pretreated nickel foam;

[0053] Step 3: Add the ZIF-67 precursor, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite to deionized water, stir well until completely dissolved to obtain solution D, and the mass ratio of ZIF-67, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite is 1:0.28:4.3:4.3:0.21:1.5;

[0054] After adding solution D and the pretreated nickel foam into a hydrothermal reaction kettle, place the hydrothermal reaction kettle in an oven and react it at a constant temperature of 180 °C for 12 hours, then cool it to room temperature in the air. Rinse the obtained solid with ethanol and deionized water 3 times (it can be rinsed with a wash bottle), put it into an oven, and dry it at 60 °C for 12 hours to obtain an electrocatalyst prepared with the ZIF-67 precursor; the mass ratio of cobalt diselenide to graphene oxide in the electrocatalyst is 1:0.28.

[0055] Example 3

[0056] Step 1: Stir 2-methylimidazole thoroughly and dissolve it completely in deionized water to obtain solution A; stir cobalt nitrate hexahydrate thoroughly and dissolve it completely in deionized water to obtain solution B; the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1:0.89, and the volume of deionized water is 4 times the total mass;

[0057] Slowly pour solution A into solution B to obtain solution C;

[0058] After reacting solution C at 25 °C for 48 hours, centrifuge, wash, and dry solution C to obtain a ZIF-67 precursor;

[0059] Step 2: Cut the nickel foam into a rectangle with dimensions of 3 cm × 1.5 cm, then place it in a first beaker containing 50 ml of alcohol, and then place the first beaker in an ultrasonic cleaner for 10 minutes; Take out the nickel foam in the first beaker and put it into a second beaker containing 50 ml of deionized water, and then place the second beaker in an ultrasonic cleaner for 10 minutes; Put the washed nickel foam into an oven and dry it at 60 °C for 12 hours to obtain the pretreated nickel foam;

[0060] Step 3: Add the ZIF-67 precursor, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite to deionized water, and stir well until completely dissolved to obtain solution D. The mass ratio of ZIF-67, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite is 1:0.65:4.3:4.3:0.21:1.5;

[0061] After adding solution D and the pretreated nickel foam into a hydrothermal reaction kettle, place the hydrothermal reaction kettle in an oven and react at a constant temperature of 180 °C for 12 hours, then cool it to room temperature in the air. Wash the obtained solid 3 times with ethanol and deionized water respectively (can be rinsed with a wash bottle), put it into an oven, and dry it at 60 °C for 12 hours to obtain an electrocatalyst prepared with ZIF-67 as the precursor; The mass ratio of cobalt diselenide to graphene oxide in the electrocatalyst is: 1:0.65.

[0062] Comparative Example 1 (Preparation of electrocatalyst without using ZIF-67 as the precursor)

[0063] Step 1: Cut the nickel foam into a rectangle with dimensions of 3 cm × 1.5 cm, then place it in a first beaker containing 50 ml of alcohol, and then place the first beaker in an ultrasonic cleaner for 10 minutes; Take out the nickel foam in the first beaker and put it into a second beaker containing 50 ml of deionized water, and then place the second beaker in an ultrasonic cleaner for 10 minutes; Put the washed nickel foam into an oven and dry it at 60 °C for 12 hours to obtain the pretreated nickel foam;

[0064] Step 2: Cobalt nitrate hexahydrate, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite were added to deionized water and stirred thoroughly until completely dissolved to obtain Solution A. The mass ratio of cobalt nitrate hexahydrate, graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite was 1:0.3:3.4:3.4:0.2:1.2;

[0065] After adding Solution A and the foam nickel treated in Step 1 into a hydrothermal reaction kettle, the hydrothermal reaction kettle was placed in an oven and reacted at a constant temperature of 180 °C for 12 h, then cooled to room temperature in air. The obtained solid was rinsed 3 times with ethanol and deionized water respectively, and then placed in an oven and dried at 60 °C for 12 h to obtain an electrocatalyst prepared without using ZIF-67 as a precursor.

[0066] Figure 2 It is the scanning electron microscope image of the electrocatalyst prepared without using ZIF-67 as a precursor. It can be seen from the figure that although the obtained cobalt diselenide is evenly dispersed, due to the absence of a precursor, the prepared catalyst has a needle-like structure, which is not as conducive to promoting the oxygen evolution reaction as the spherical structure in Example 1.

[0067] Comparative Example 2 (Preparation of an electrocatalyst using ZIF-67 as a precursor but without adding graphene oxide)

[0068] Step 1: 2-Methylimidazole was stirred thoroughly and completely dissolved in deionized water to obtain Solution A. Cobalt nitrate hexahydrate was stirred thoroughly and completely dissolved in deionized water to obtain Solution B. The molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate was 4:1, and the volume of deionized water was 4 times the total mass;

[0069] Solution A was slowly poured into Solution B to obtain Solution C;

[0070] After reacting Solution C at 25 °C for 48 h, Solution C was centrifuged, washed, and dried to obtain a ZIF-67 precursor;

[0071] Step 2: The foam nickel was cut into a rectangle with a size of 3 cm × 1.5 cm, then placed in a first beaker containing 50 ml of alcohol, and the first beaker was placed in an ultrasonic cleaner for 10 min; the foam nickel in the first beaker was taken out and placed in a second beaker containing 50 ml of deionized water, and the second beaker was placed in an ultrasonic cleaner for 10 min; the washed foam nickel was placed in an oven and dried at 60 °C for 12 h to obtain pretreated foam nickel;

[0072] Step 3: Add ZIF-67 precursor, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite into deionized water, and stir thoroughly until completely dissolved to obtain solution D. The mass ratio of ZIF-67, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite is 1:4.3:4.3:0.21:1.5;

[0073] After adding solution D and the nickel foam treated in step 2 into a hydrothermal reaction kettle, place the hydrothermal reaction kettle in an oven and react at a constant temperature of 180 °C for 12 h. Then cool it to room temperature in air. Wash the obtained solid with ethanol and deionized water three times respectively, and then place it in an oven and dry it at 60 °C for 12 h to obtain an electrocatalyst prepared with ZIF-67 as the precursor without adding graphene oxide.

[0074] Figure 3 It is the scanning electron microscope image of the electrocatalyst prepared in Comparative Example 2. It can be seen from the figure that due to the absence of graphene oxide in the synthesis process, the prepared electrocatalyst agglomerates, which further covers the active sites of the electrocatalyst, ultimately resulting in the electrocatalytic performance not meeting the expectations.

[0075] Figure 4 It is the comparison chart of oxygen evolution curves of the electrocatalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2. When the current density is 10 mA / cm -2 , the lower the potential value of the electrocatalyst, the better the electrocatalytic performance.

[0076] The test conditions for obtaining the oxygen evolution curve: Perform linear sweep voltammetry test at 5 mV / s.

[0077] Figure 5 It is the stability performance diagram of the electrocatalyst prepared in Example 1. It can be seen from the figure that the potential value of the electrocatalyst remains basically unchanged after 24 h of constant current polarization, indicating that the electrocatalytic performance of the electrocatalyst for the oxygen evolution reaction remains basically unchanged after a long-time reaction.

[0078] The test conditions for obtaining the stability curve: Perform constant current polarization test at a current density of 10 mA / cm -2 .

[0079] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited by the technical solutions described in the embodiments of the present invention. Those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced to achieve the same technical effects; as long as it meets the usage requirements, it is within the protection scope of the present invention.

Claims

1. A cobalt diselenide / reduced graphene oxide electrocatalyst, characterized in that Nickel foam is used to support cobalt diselenide and graphene oxide.

2. A cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 1, characterized in that The mass ratio of the cobalt diselenide to graphene oxide is 1:0.1-0.

8.

3. A cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 1, characterized in that The mass ratio of the cobalt diselenide to graphene oxide is 1:0.28, 1:0.46 or 1:0.

65.

4. A method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst, characterized in that The following steps are involved: Step 1: Mixing a 2-methylimidazole solution with a cobalt nitrate hexahydrate solution, stirring, cooling to room temperature after the reaction, and centrifuging, washing, and drying the obtained product in sequence to obtain a ZIF-67 precursor; Step 2: Cleaning the nickel foam with alcohol and deionized water in an ultrasonic cleaner in sequence and then drying it to obtain a pretreated nickel foam; Step 3: The ZIF-67 precursor is dispersed in water, and graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride, and sodium selenite are added to the solution and mixed. The mixed solution and nickel foam are placed in a hydrothermal reactor for hydrothermal reaction. The reaction product is rinsed with deionized water and ethanol in turn and then dried to obtain an electrocatalyst.

5. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that The step 1: mixing a 2-methylimidazole solution with a cobalt nitrate hexahydrate solution, performing constant temperature mechanical stirring or magnetic stirring at 0-100° C., a rotor speed of 500 rpm to 1000 rpm, reacting for 24-72 hours, and then cooling to room temperature; The centrifugation and washing are both carried out using a centrifuge. The centrifugation process is to directly put the reaction solution into a centrifuge tube and then centrifuge it in a centrifuge; the washing process is to add deionized water or ethanol to the powder obtained after centrifugation and centrifuge it again to remove residual impurities; the centrifuge speed of the centrifuge and washing process is 4000 rpm to 8000 rpm, the centrifugation time is 3 min to 7 min; the number of washing times is 2 to 4 times; The drying temperature is 5° C. to 100° C., and the drying time is 8 hours to 72 hours.

6. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that In the step 1, the concentration of the 2-methylimidazole solution is 0.01 mol / L to 1 mol / L, and the concentration of the cobalt nitrate hexahydrate solution is 0.01 mol / L to 1 mol / L.

7. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that In the step 1, the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1:0.1-1.

0.

8. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that Step 2: Cut the nickel foam into 3cm pieces 2 ~9cm 2 Afterwards, the nickel foam is placed in a first container filled with alcohol, and the first container is placed in an ultrasonic cleaner for cleaning for 5 minutes to 30 minutes; the nickel foam in the first container is taken out and placed in a second container filled with deionized water, and the second container is placed in an ultrasonic cleaner for cleaning for 5 minutes to 30 minutes; and then dried for 8 hours to 72 hours to obtain the pretreated nickel foam.

9. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that In the step 3, the concentration of the dispersion of the ZIF-67 precursor in water is 0.01 mol / L to 0.10 mol / L.

10. The method for preparing a cobalt diselenide / reduced graphene oxide electrocatalyst according to claim 4, characterized in that In step 3, the mass ratio of the ZIF-67 precursor to graphene oxide, sodium hydroxide, ethylenediaminetetraacetic acid, sodium borohydride and sodium selenite is 1:0.1-5.0:0.1-5.0:0.1-5.0:0.1-5.0:0.1-5.0.

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