Preparation method of diatomic catalyst composite electrode, diatomic catalyst composite electrode and application of diatomic catalyst composite electrode

Abstract

The invention discloses a preparation method of a double-atom catalyst composite electrode, the double-atom catalyst composite electrode and application of the double-atom catalyst composite electrode, and belongs to the technical field of energy storage. The method comprises the following steps: (1) obtaining an alcoholic solution of zinc nitrate, and recording the alcoholic solution as a solution A; (2) obtaining an alcoholic solution of 2-methylimidazole, and recording the alcoholic solution as a solution B; (3) stirring a mixture containing the solution A, the solution B and the carbon substrate to obtain a ZIF-8 loaded carbon substrate; (4) sequentially carrying out washing, drying and high-temperature calcination on the ZIF-8 loaded carbon substrate to obtain a calcined product; (5) putting the calcined product into a mixed solution of silver salt and tin salt, standing, taking out and drying to obtain a dried product; and (6) carrying out secondary high-temperature calcination on the dried product to obtain the diatomic catalyst composite electrode. The preparation method provided by the invention is simple and easy to control, and has relatively high electrocatalytic activity and cycling stability and an excellent hydrogen evolution inhibition effect.

Description

Technical Field

[0001] The present application belongs to the field of energy storage technology, and in particular relates to a method for preparing a diatomic catalyst composite electrode, the diatomic catalyst composite electrode and applications thereof. Background Art

[0002] In recent years, society is in a stage of rapid development, and the consumption of fossil energy is increasing, which has brought serious environmental pollution. This calls for people to make full use of renewable energy. However, due to the intermittent and volatile nature of renewable energy, more than 20% of renewable energy cannot be stored, which has also caused serious damage to the stability of the power grid. This urgently requires large-scale energy storage technology. Among the many energy storage technologies, all-vanadium liquid flow batteries have gradually been applied in the field of large-scale energy storage technology due to their flexible design, high safety, high energy efficiency and low cost potential. However, the cost of the battery stack and vanadium salts limits the commercial use of all-vanadium liquid flow batteries. An effective way is to enable all-vanadium liquid flow batteries to operate at higher current density while maintaining higher energy density to reduce the cost of the battery stack, but the increase in current density will lead to increased battery polarization, resulting in a decrease in battery performance.

[0003] As one of the key components of all-vanadium liquid flow batteries, electrodes are closely related to the activation polarization, ohmic polarization and concentration polarization of batteries. Currently, commonly used electrodes are graphite felt and carbon felt, mainly because they have good conductivity, stability and low cost. However, when operating at higher current density, the lack of sufficiently high specific surface area and hydrophilicity will lead to greater polarization losses. Therefore, it is necessary to modify the electrodes to improve the catalytic activity, hydrophilicity and stability of the electrodes.

[0004] At present, the modification methods of electrodes mainly include surface functionalization, which improves the hydrophilicity of the electrode surface through oxidation, nitridation and other treatments, but anchoring oxygen in a wider voltage window is still a problem; surface structure regulation, which increases the specific surface area of ​​the electrode through etching methods such as KOH and NiO, but this will damage the mechanical properties of the electrode; loading carbon-based catalysts with large specific surface areas such as carbon nanotubes and mesoporous carbon can reduce the activation polarization to a certain extent, but the pore structure is relatively fragile and cannot meet the long-term stable operation of the battery; directly loading metal catalysts, loading metal catalysts such as Pt, Pd, and Ag, although it will improve its electrocatalytic activity to a certain extent, it will produce serious hydrogen evolution side reactions, and loading Bi, Sn, and Pb can play a good role in inhibiting hydrogen evolution, but its electrocatalytic activity is insufficient. In addition, metal catalysts are also limited by particle size, distribution uniformity and structural stability, which will greatly reduce the electrocatalytic activity and stability of metal catalysts. Therefore, how to prepare metal catalysts with high activity, high hydrogen evolution overpotential and high stability has become an urgent problem to be solved today. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a method for preparing a diatomic catalyst composite electrode, the diatomic catalyst composite electrode and its application. The method uses graphite felt and other materials as a substrate to in-situ load ZIF-8, then performs carbonization treatment, and uses its microporous structure to adsorb Ag through a liquid phase impregnation process. + and Sn 2+ In the later high-temperature calcination and carbonization process, the nitrogen atoms in the precursor are used to anchor Ag and Sn atoms to form N 4 -Ag-Sn-N 4 The coordination structure enables Ag and Sn atoms to be stably dispersed on the ZIF-8 sintered carbon substrate, thereby preparing an Ag / Sn diatomic catalyst with high catalytic activity, high hydrogen evolution overpotential and high stability. The preparation method provided in this application is simple and easy to control, and has high electrocatalytic activity, excellent hydrogen evolution inhibition effect and high cycle stability, and is expected to achieve large-scale commercial production.

[0006] In order to achieve the above-mentioned invention object, this application provides the following technical solutions:

[0007] On the one hand, the present application provides a method for preparing a diatomic catalyst composite electrode, comprising the following steps:

[0008] (1) obtaining an alcohol solution of zinc nitrate, referred to as solution A;

[0009] (2) obtaining an alcohol solution of 2-methylimidazole, referred to as solution B;

[0010] (3) stirring a mixture containing the A solution, the B solution, and the carbon substrate to obtain a carbon substrate loaded with ZIF-8;

[0011] (4) washing, drying, and high-temperature calcining the carbon substrate loaded with ZIF-8 in sequence to obtain a calcined product;

[0012] (5) placing the calcined product in a mixed solution of a silver salt and a tin salt, allowing the mixture to stand, taking it out and drying it to obtain a dried product;

[0013] (6) The dried product is subjected to secondary high-temperature calcination to obtain the diatomic catalyst composite electrode.

[0014] Optionally, in step (1), the alcohol is methanol;

[0015] The usage ratio of the zinc nitrate and methanol is 2-7 g:50-300 mL.

[0016] Optionally, in step (2), the alcohol is methanol;

[0017] The usage ratio of the 2-methylimidazole and methanol is 4-15 g:50-300 mL.

[0018] Optionally, in step (3), the mixture comprises the following components in parts by weight: 1 to 4 parts by weight of solution A, 1 to 8 parts by weight of solution B, and 1 to 15 parts by weight of a carbon substrate.

[0019] Optionally, in step (3), the carbon substrate includes at least one of graphite felt, carbon felt, carbon cloth, and carbon paper.

[0020] Optionally, in step (3), the thickness of the carbon substrate is 1 to 5 mm, and the surface area of ​​the two side surfaces of the carbon substrate is 5 to 20 cm 2 .

[0021] Optionally, step (3) comprises: immersing the carbon substrate in solution A, then pouring solution B into solution A, and stirring to obtain a carbon substrate loaded with ZIF-8.

[0022] Optionally, the soaking time is 1 to 2 hours;

[0023] The stirring time is 12 to 36 hours.

[0024] Optionally, the soaking time is independently selected from any value among 1 h, 1.2 h, 1.5 h, 1.7 h, 2 h, or any range between two values.

[0025] Optionally, the stirring time is independently selected from any value among 12h, 15h, 18h, 20h, 22h, 25h, 28h, 30h, 32h, 34h, 36h, or any range between two of them.

[0026] Optionally, in step (4), the washing is performed by ethanol washing.

[0027] Optionally, in step (4), the drying temperature is 60 to 80° C.;

[0028] The drying time is 3 to 6 hours.

[0029] Optionally, in step (4), the drying temperature is independently selected from any value among 60°C, 65°C, 70°C, 75°C, 80°C, or any range between two of them.

[0030] Optionally, in step (4), the drying time is independently selected from any value among 3h, 4h, 5h, 6h or any range between two of them.

[0031] Optionally, in step (4), the high-temperature calcination is carried out in an inert gas atmosphere;

[0032] The inert gas includes nitrogen and / or argon;

[0033] The temperature of the high temperature calcination is 800-1300°C;

[0034] The high temperature calcination time is 0.5 to 3 hours.

[0035] Optionally, in step (4), the temperature of the high temperature calcination is independently selected from any value among 800°C, 850°C, 900°C, 950°C, 1000°C or any range between two values.

[0036] Optionally, in step (4), the high temperature calcination time is independently selected from any value among 0.5h, 1h, 2h, 3h or any range between the two.

[0037] Optionally, in step (5), the silver salt is at least one of silver nitrate, silver oxalate, and silver perchlorate;

[0038] The tin salt is at least one of stannous chloride, stannous oxalate and stannous benzoate.

[0039] Optionally, in step (5), the molar concentration of the mixed solution is 0.005 to 3 mol / mL.

[0040] Optionally, in step (5), the molar concentration of the mixed solution is independently selected from any value among 0.005 mol / mL, 0.01 mol / mL, 0.1 mol / mL, 0.5 mol / mL, 1 mol / mL, 2 mol / mL, 3 mol / mL or any range between two values.

[0041] Optionally, in step (5), the mixed solution comprises the following components in parts by weight: 1 to 4 parts by weight of silver salt and 1 to 8 parts by weight of tin salt.

[0042] Optionally, in step (5), the standing time is 12 to 24 hours.

[0043] Optionally, in step (5), the standing time is independently selected from any value among 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a range between any two of them.

[0044] Optionally, in step (5), the drying temperature is 50 to 150° C.;

[0045] The drying time is 3 to 12 hours.

[0046] Optionally, in step (6), the secondary high-temperature calcination is carried out in an inert gas atmosphere;

[0047] The inert gas includes nitrogen and / or argon;

[0048] The temperature of the secondary high temperature calcination is 600-1000°C;

[0049] The time of the secondary high-temperature calcination is 30 to 180 minutes.

[0050] In a second aspect, the present application provides a diatomic catalyst composite electrode prepared by the above preparation method.

[0051] Optionally, the loading amount of the diatomic catalyst composite electrode is 1 to 5 mg / cm 2 .

[0052] In a third aspect, the present application provides the use of the above-mentioned diatomic catalyst composite electrode as a negative electrode material.

[0053] In a fourth aspect, the present application provides the use of the above-mentioned diatomic catalyst composite electrode in the preparation of an all-vanadium liquid flow battery.

[0054] Optionally, the current density of the double-atom catalyst composite electrode is 80-280 mA / cm 2 .

[0055] Compared with the prior art, this application has the following beneficial effects:

[0056] (1) The present application provides a method for preparing a diatomic catalyst composite electrode, which makes full use of the excellent electrocatalytic activity of Ag metal catalyst and the excellent hydrogen evolution inhibition effect of Sn metal catalyst; the present application uses graphite felt as a substrate to in-situ load ZIF-8, then performs carbonization treatment, and uses its microporous structure to adsorb Ag through a liquid phase impregnation process. + and Sn 2+ Later, high temperature calcination is performed again to use the nitrogen atoms to anchor the Ag and Sn atoms to form N 4 -Ag-Sn-N 4 The coordination structure enables Ag and Sn atoms to be stably dispersed on the ZIF-8 sintered carbon substrate, thereby preparing an Ag / Sn diatomic catalyst with high catalytic activity, high hydrogen evolution overpotential and high stability; the preparation method of the present application is simple and easy to control, the production equipment is conventional, and it is suitable for large-scale production.

[0057] (2) The diatomic catalyst composite electrode provided in this application has N 4 -Ag-Sn-N 4 The coordination structure not only has excellent electrocatalytic activity, but also has a significant inhibitory effect on hydrogen evolution and high cycle stability. It can significantly reduce electrode polarization and promote the efficient and stable redox reaction of vanadium ions. 2The energy efficiency can reach 81.3%. During 1500 cycles, the energy efficiency is almost attenuated, which can meet practical applications.

[0058] (3) The diatomic catalyst composite electrode provided in this application can be used as a negative electrode material in the preparation process of all-vanadium liquid flow batteries, effectively improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 This is a SEM image of the Ag / Sn diatomic catalyst composite electrode prepared in Example 1 of the present application;

[0061] Figure 2 This is the HAADF-STEM image of the Ag / Sn diatomic catalyst prepared in Example 1 of the present application (Note: the scale is 2 nm);

[0062] Figure 3 CV test images of Ag / Sn diatoms, Sn single atoms and Ag single atoms for this application. DETAILED DESCRIPTION

[0063] The present application is further described below in conjunction with specific embodiments. The following are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application discloses the following preferred embodiments, they are not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make some changes or modifications are equivalent to equivalent implementation cases and are within the scope of the technical solution.

[0064] Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources and used directly without any special treatment.

[0065] Unless otherwise specified, the analysis methods in the examples all adopt conventional settings and conventional analysis methods of instruments or equipment.

[0066] Example 1

[0067] (1) Obtain solution A: add 3.5 g of zinc nitrate hexahydrate into 150 ml of methanol and stir;

[0068] To obtain solution B: add 7 g of 2-methylimidazole to 150 ml of methanol and stir;

[0069] (2) Graphite felt (thickness 2 mm, surface area of ​​both sides 12 cm) 2 ) was placed in solution A and soaked for 2 h, then solution B was poured into solution A and slowly stirred for 24 h to obtain graphite felt loaded with ZIF-8;

[0070] (3) The obtained graphite felt loaded with ZIF-8 was rinsed three times with methanol, and then dried at 60°C for 6 h. The dried sample was calcined at 1100°C in argon for 1 h, with a heating rate of 5°C / min to the calcination temperature;

[0071] (4) Place the obtained sample into 100 ml of silver salt and tin salt solution with a concentration of 0.01 mol / ml and let it stand for 12 hours;

[0072] (5) The sample was taken out and dried at 60°C for 6 h, and then calcined again at 900°C in a nitrogen atmosphere for 2 h to obtain a graphite felt electrode loaded with Ag / Sn diatomic catalyst, with a catalyst loading of 2 mg / cm 2 The preparation method provided by the present invention is simple and easy to control, the electrode structure is controllable, and it has excellent electrochemical activity, significant hydrogen evolution inhibition effect and high cycle stability.

[0073] Performance test: The assembled all-vanadium liquid flow battery consists of three parts: positive and negative electrolyte storage tanks, pumps and single cells. The positive and negative electrolytes are both 0.8MV 3+ +0.8MV 4+ +3M H 2 SO 4 The amount of electrolyte is 3.5ml / cm 2 In a single cell, the graphite felt electrode loaded with the catalyst obtained above is used as the negative electrode of the battery, and the graphite felt is used as the positive electrode of the battery. The electrode thickness is 2 mm, and the surface area of ​​the two sides of the electrode is 12 cm 2 ; Nafion 212 membrane is the middle diaphragm, at 80~280mA / cm 2 The battery was charged and discharged at a constant current density of 1.55V, and the discharge cut-off voltage was 1.0V. At room temperature, the charge and discharge performance was tested using an Arbin charge and discharge instrument.

[0074] from Figure 1 and Figure 2 It can be seen that the graphite felt is loaded with Ag / Sn diatomic catalysts, and the size of the Ag / Sn diatomic catalysts is Evenly dispersed on the carbon substrate formed by ZIF-8. Figure 3 It can be seen that the Ag / Sn diatomic catalyst has higher electrocatalytic activity than the Sn single atom catalyst, and has a higher hydrogen evolution overpotential than the Ag single atom catalyst.

[0075] It can be seen from Table 1 that the prepared electrode has a 2 , the energy efficiency reaches 81.32%.

[0076] Example 2

[0077] The preparation method, process and performance test process are the same as those in Example 1, except that step (5) is again subjected to high-temperature calcination at 800° C. in a nitrogen atmosphere for 2 h.

[0078] Example 3

[0079] The preparation method, process and performance test process are the same as those in Example 1, except that step (5) is again subjected to high-temperature calcination at 1000° C. for 2 h in a nitrogen atmosphere.

[0080] Example 4

[0081] The preparation method, process and performance test process are the same as those in Example 1, except that the concentration of the silver salt and tin salt added in step (4) is 0.05 mol / ml.

[0082] Example 5

[0083] The preparation method, process and performance test process are the same as those in Example 1, except that the concentration of the silver salt and tin salt added in step (4) is 0.02 mol / ml.

[0084] Comparative Example 1

[0085] The preparation method, process and performance test process are the same as those in Example 1, except that in step (4), only silver salt is added at a concentration of 0.01 mol / ml.

[0086] Comparative Example 2

[0087] The preparation method, process and performance test process are the same as those in Example 1, except that in step (4), only tin salt is added at a concentration of 0.01 mol / ml.

[0088] Comparative Example 3

[0089] (1) Obtain solution A: add 3.5 g of zinc nitrate hexahydrate into 150 ml of methanol and stir;

[0090] To obtain solution B: add 7 g of 2-methylimidazole to 150 ml of methanol and stir;

[0091] (2) Soak the graphite felt in solution A for 2 h, pour solution B into solution A, and slowly stir for 24 h to obtain graphite felt loaded with ZIF8;

[0092] (3) The obtained ZIF8-loaded graphite felt was rinsed with methanol for more than three times, and then dried at 60°C for 6 h. The dried sample was calcined at 1100°C in argon for 1 h at a heating rate of 5°C / min to obtain a composite electrode supported by a ZIF-8-derived carbon material.

[0093] The performance test process is the same as that of Example 1. As can be seen from Table 1, the prepared electrode has a 2 , the energy efficiency reaches 74.83%.

[0094] Comparative Example 4

[0095] (1) Wash and dry the flake graphite felt electrode; the specific operation of washing is: 2 The graphite felt sheet (electrode thickness 2 mm) was rinsed three times with deionized water and then washed three times with anhydrous ethanol, and then ultrasonically cleaned in an ethanol-water solution with a volume ratio of 1:1 for 40 min;

[0096] (2) Drying treatment: The specific operation is: placing the cleaned graphite felt in a vacuum drying oven at 80°C for 4 hours to obtain a dried graphite felt electrode;

[0097] (3) The dried graphite felt electrode is used as the negative electrode. The assembled all-vanadium liquid flow battery consists of three parts: positive and negative electrode electrolyte storage tanks, pumps and single cells. The positive and negative electrode electrolytes are both 0.8MV 3+ +0.8MV 4+ +3M H 2 SO 4 , the amount of electrolyte is 3.5ml / cm 2 The graphite felt electrodes obtained in the single cell are used as positive and negative electrodes, the electrode thickness is 2 mm, and the surface area of ​​the two sides of the electrode is 12 cm 2 ; Nafion 212 membrane is the middle diaphragm, at 80~280mA / cm 2 The battery is charged and discharged at a constant current density of , and the charge and discharge cut-off voltage is 1.55V, and the discharge cut-off voltage is 1.0V.

[0098] As can be seen from Table 1, the prepared electrode can only be opened to 120 mA / cm 2 .

[0099] Comparative Example 5

[0100] (1) Clean and dry the sheet carbon felt electrode; the specific cleaning operation is: 2 The sheet carbon felt (electrode thickness 2 mm) was rinsed three times with deionized water and then washed three times with anhydrous ethanol, and then ultrasonically cleaned in an ethanol-water solution with a volume ratio of 1:1 for 40 min;

[0101] (2) Drying treatment: The specific operation is: placing the cleaned graphite felt in a vacuum drying oven at 80°C for 4 hours to obtain a dried graphite felt electrode;

[0102] (3) The dried carbon felt electrode is used as the negative electrode. The assembled all-vanadium liquid flow battery consists of three parts: positive and negative electrolyte storage tanks, pumps and single cells. The positive and negative electrolytes are both 0.8MV 3+ +0.8MV 4+ +3M H 2 SO 4 , the amount of electrolyte is 3.5ml / cm 2 The graphite felt electrodes obtained in the single cell are used as positive and negative electrodes, the electrode thickness is 2 mm, and the surface area of ​​the two sides of the electrode is 12 cm 2 ; Nafion 212 membrane is the middle diaphragm, at 80~280mA / cm 2 The battery is charged and discharged at a constant current density of , and the charge and discharge cut-off voltage is 1.55V, and the discharge cut-off voltage is 1.0V.

[0103] It can be seen from Table 1 that the prepared electrode has a 2 , the energy efficiency reaches 77.50%.

[0104] Table 1 Current density is 200mA / cm 2 Battery performance comparison

[0105]

[0106] Among them, electrolyte utilization = (discharge capacity / theoretical capacity*100%)

[0107] Combined with Table 1, it can be seen that in Example 1, the carbon sintered by ZIF-8 adsorbing silver salt and tin salt was sintered at 900°C for 2h in a nitrogen atmosphere, and Ag and Sn atoms formed N 4 -Ag-Sn-N 4 The coordination structure can be evenly and stably dispersed on the carbon substrate, with high catalytic activity, high hydrogen evolution overpotential and high stability; in Comparative Example 1, adding only silver salt will cause serious hydrogen evolution side reaction and decreased coulombic efficiency; in Comparative Example 2, adding only tin salt will cause insufficient electrochemical activity and decreased performance; in Comparative Example 3, the pure carbon-based catalyst cannot provide enough reactive sites, resulting in decreased battery performance; in Comparative Example 4, the graphite felt electrode without supported catalyst has low electrochemical activity and poor performance; in Comparative Example 5, the carbon felt has poor operating performance at higher current density and cannot meet actual commercial applications. It can be confirmed from the above that the silver / tin diatomic catalyst composite electrode of the present application can significantly improve the electrochemical activity of vanadium active material, inhibit hydrogen evolution side reaction, improve the power density of the battery and further promote the commercialization of all-vanadium liquid flow battery.

[0108] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a diatomic catalyst composite electrode, It is characterized in that The steps include: (1) obtaining an alcohol solution of zinc nitrate, referred to as solution A; (2) obtaining an alcohol solution of 2-methylimidazole, referred to as solution B; (3) stirring a mixture containing the A solution, the B solution, and the carbon substrate to obtain a carbon substrate loaded with ZIF-8; (4) washing, drying, and high-temperature calcining the carbon substrate loaded with ZIF-8 in sequence to obtain a calcined product; (5) placing the calcined product in a mixed solution of a silver salt and a tin salt, allowing the mixture to stand, taking it out and drying it to obtain a dried product; (6) The dried product is subjected to secondary high-temperature calcination to obtain the diatomic catalyst composite electrode.

2. The method for preparing a diatomic catalyst composite electrode according to claim 1, It is characterized in that In step (1), the alcohol is methanol; The dosage ratio of the zinc nitrate and methanol is 2-7 g:50-300 mL; Preferably, in step (2), the alcohol is methanol; The usage ratio of the 2-methylimidazole and methanol is 4-15 g:50-300 mL.

3. The method for preparing a diatomic catalyst composite electrode according to claim 1, It is characterized in that In step (3), the mixture comprises the following components in parts by weight: 1 to 4 parts by weight of solution A, 1 to 8 parts by weight of solution B, and 1 to 15 parts by weight of a carbon substrate; Preferably, in step (3), the carbon substrate comprises at least one of graphite felt, carbon felt, carbon cloth, and carbon paper; Preferably, in step (3), the thickness of the carbon substrate is 1 to 5 mm, and the surface area of ​​the two side surfaces of the carbon substrate is 5 to 20 cm 2 ; Preferably, step (3) comprises: soaking the carbon substrate in solution A, then pouring solution B into solution A, stirring, to obtain a carbon substrate loaded with ZIF-8; Preferably, the soaking time is 1 to 2 hours; The stirring time is 12 to 36 hours.

4. The method for preparing a diatomic catalyst composite electrode according to claim 1, It is characterized in that In step (4), the washing is performed by ethanol washing; Preferably, in step (4), the drying temperature is 60 to 80°C; The drying time is 3 to 6 hours; Preferably, in step (4), the high-temperature calcination is carried out in an inert gas atmosphere; The inert gas includes nitrogen and / or argon; The temperature of the high temperature calcination is 800-1300°C; The high temperature calcination time is 0.5 to 3 hours.

5. The method for preparing a diatomic catalyst composite electrode according to claim 1, It is characterized in that In step (5), the silver salt is at least one of silver nitrate, silver oxalate, and silver perchlorate; The tin salt is at least one of stannous chloride, stannous oxalate and stannous benzoate; Preferably, in step (5), the molar concentration of the mixed solution is 0.005 to 3 mol / mL; Preferably, in step (5), the mixed solution comprises the following components in parts by weight: 1 to 4 parts by weight of a silver salt, and 1 to 8 parts by weight of a tin salt; Preferably, in step (5), the standing time is 12 to 24 hours; Preferably, in step (5), the drying temperature is 50 to 150°C; The drying time is 3 to 12 hours.

6. The method for preparing a diatomic catalyst composite electrode according to claim 1, It is characterized in that In step (6), the secondary high-temperature calcination is carried out in an inert gas atmosphere; The inert gas includes nitrogen and / or argon; The temperature of the secondary high temperature calcination is 600-1000°C; The time of the secondary high-temperature calcination is 30 to 180 minutes.

7. A diatomic catalyst composite electrode prepared by the preparation method according to any one of claims 1 to 6.

8. The diatomic catalyst composite electrode according to claim 7, It is characterized in that The loading amount of the double-atom catalyst composite electrode is 1 to 5 mg / cm 2 .

9. Use of the diatomic catalyst composite electrode according to claim 7 or 8 as a negative electrode material.

10. Use of the diatomic catalyst composite electrode according to claim 7 or 8 in the preparation of an all-vanadium liquid flow battery; Preferably, the current density of the double-atom catalyst composite electrode is 80-280 mA / cm 2 .

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