Catalytic modified graphite felt electrode for vanadium battery and preparation method

Abstract

The invention relates to the technical field of all-vanadium redox flow battery electrode materials, and discloses a catalytic modified graphite felt electrode for a vanadium battery and a preparation method of the catalytic modified graphite felt electrode. Aiming at the problems that an existing graphite felt electrode is high in hydrophobicity, insufficient in catalytic activity, infirm in loading of carbon nano tubes and the like, the method is improved through the following steps that S1, graphite felt is subjected to acid pretreatment; s2, modifying the graphite felt with polypyrrole; s3, modifying the graphite felt by using carbon nanotubes; and S4, catalytically modifying the graphite felt. According to the catalytic modified graphite felt prepared by the invention, carboxyl carbon nanotubes are uniformly loaded on a polypyrrole layer through hydrogen bonds and pi-pi conjugation, and the conductivity is improved through a sintering process. In addition, polypyrrole particles are further grown on the surfaces of the carbon nanotubes by utilizing the electrostatic interaction of a surfactant, so that active sites are increased. Through in-situ growth of polypyrrole and composite loading of carbon nanotubes, sintering optimization and surfactant regulation are combined, so that the conductivity, catalytic activity and washing resistance of the electrode are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite felt electrodes for all-vanadium redox flow batteries, and particularly to a catalytically modified graphite felt electrode for vanadium batteries and a preparation method thereof. Background Art

[0002] The performance of all-vanadium redox flow batteries (VFBs) highly depends on electrodes, diaphragms, and electrolytes. In recent years, researchers have been committed to developing high-performance electrode materials. Generally, VFB electrode materials can be divided into noble metal materials (such as Pt-Ti, IrO2-DSA) and carbon-based materials (CBMs). Although noble metal electrodes have excellent electrochemical activity and reversibility, their high costs limit their widespread applications. Carbon-based materials are regarded as the most feasible electrode materials for VFBs due to their chemical inertness and rich resources. Among them, self-supporting carbon-based materials (such as graphite felt, carbon felt, carbon cloth) can be directly used as electrodes without complex processing. Graphite felt (GF) is considered the most potential electrode material due to its high stability, low cost, and high conductivity. However, GF has problems of poor electrolyte wettability and insufficient active sites due to its high hydrophobicity and low specific surface area caused by high graphitization temperature.

[0003] Traditional modification methods (such as acid treatment, thermal oxidation, electrochemical activation, etc.) can improve the hydrophilicity of GF, but the improvement of VFB performance is limited. In recent years, the strategy of preparing composite electrodes by loading nanotubes and conductive polymers on the surface of GF has attracted much attention. Common loading methods include: impregnation-drying method and chemical vapor deposition method. However, the impregnation-drying method only adsorbs conductive materials on the surface of carbon fibers through van der Waals forces, and the binding force is not strong, and it is easy to fall off under the flow scouring of the electrolyte; while the chemical vapor deposition method grows in-situ on the surface of carbon fibers, and the carbon nanotubes are unevenly dispersed, and this development and preparation process is complex, resulting in a significant increase in the cost of electrode materials and being unsuitable for large-scale industrial production. In addition, there is still a large room for improvement in the catalytic activity of GF electrodes, and further improvement is urgently needed. Summary of the Invention

[0004] The present invention aims to solve the above technical problems and provides a catalytically modified graphite felt electrode for vanadium batteries and a preparation method thereof.

[0005] The technical solution adopted by the present invention is as follows: The present application discloses a preparation method of a catalytically modified graphite felt electrode for vanadium batteries, including the following steps: Step S1: Acid pretreatment of graphite felt: Immerse the graphite felt in a concentrated sulfuric acid solution with a mass fraction of 98%, wash with deionized water, and vacuum dry to obtain acid-pretreated graphite felt.

[0006] Step S2: Preparation of polypyrrole-modified graphite felt: Add 3 - 5 parts by mass of pyrrole monomer into a mixed solution of 100 parts by mass of deionized water and ethanol, then add 1 - 3 parts by mass of acid-pretreated graphite felt, and finally slowly add 10 - 20 parts by mass of initiator solution. Turn on the circulation pump for circulating dispersion. After the reaction, wash with water and ethanol and then dry under vacuum to obtain polypyrrole-modified graphite felt.

[0007] Step S3: Preparation of carbon nanotube-modified graphite felt: Ultrasonically disperse 1 - 2 parts by mass of carboxyl carbon nanotubes, 0.5 - 1 part by mass of dispersant polyvinylpyrrolidone and 100 parts by mass of deionized water for 1 - 2 h, then transfer to a reactor. Add the polypyrrole-modified graphite felt into the reactor, turn on the circulation pump for circulating dispersion, blend and sinter to obtain carbon nanotube-modified graphite felt.

[0008] Step S4: Preparation of catalytically modified graphite felt: Disperse 1 - 2 parts by mass of surfactant and 0.5 - 2 parts by mass of pyrrole monomer in 100 parts by mass of deionized water, add the carbon nanotube-modified graphite felt, adjust the pH value with hydrochloric acid, drop 10 - 20 parts by mass of initiator solution into the reactor, turn on the circulation pump for circulating dispersion. After the reaction, wash with water and ethanol and then dry under vacuum to obtain catalytically modified graphite felt.

[0009] Preferably, in step S1, the soaking temperature is 25 - 40 °C and the soaking time is 8 - 10 h.

[0010] Preferably, in the mixed solution of step S2, the mass ratio of deionized water to ethanol is (20~50):1.

[0011] Preferably, in step S2, the reaction temperature is -5 - 3 °C and the reaction time is 16 - 20 h.

[0012] Preferably, in steps S2 and S4, the initiator is at least one of ammonium persulfate, sodium persulfate and potassium persulfate, and the mass fraction of the initiator solution is 1 - 2%.

[0013] Preferably, in step S3, the blending temperature is 60 - 80 °C and the blending time is 2 - 4 h.

[0014] Preferably, the sintering method in step S3 is to place it in a muffle furnace, with a heating rate of 2 - 10 °C / min, heat up to 450 - 500 °C, and keep warm for 2 - 4 h.

[0015] Preferably, in step S4, the surfactant is at least one of cetyl dimethyl ammonium chloride, octadecyl trimethyl ammonium chloride and dodecyl dimethyl amine oxide.

[0016] Preferably, in step S4, the pH value is 4 - 6; the reaction temperature is 0 - 3 °C and the reaction time is 18 - 24 h.

[0017] The present invention also discloses a catalytically modified graphite felt electrode for a vanadium battery, which is prepared by using the above-mentioned preparation method of a catalytically modified graphite felt electrode for a vanadium battery.

[0018] The beneficial effects of the present invention are as follows: 1. The catalytically modified graphite felt electrode prepared by the present invention grafts polypyrrole on the graphite felt fibers by an in-situ growth method. As a conductive binder, polypyrrole binds carbon nanotubes to the graphite felt fibers through hydrogen bonding and π-π conjugation. The carbon nanotubes are evenly loaded and have a high loading amount. While being resistant to scouring, a conductive network is constructed, improving the catalytic activation ability of the electrode, and further improving the battery energy, voltage efficiency, and capacity retention ability.

[0019] 2. Through the sintering process of the present invention, part of the dispersant polyvinylpyrrolidone is carbonized, which improves the conductivity while maintaining the bonding force of the carbon nanotube-modified graphite felt, and further improves the energy and voltage efficiency of the battery.

[0020] 3. The catalytically modified graphite felt electrode prepared by the present invention enables polypyrrole particles to grow on the carbon nanotubes through the electrostatic interaction between the surfactant and carboxylated carbon nanotubes, increasing the reaction active area and active sites, providing faster ion transport and lower resistance, further enhancing the catalytic activity of the electrode, and significantly improving the battery energy and voltage efficiency.

[0021] 4. The strength of the catalytically modified graphite felt fiber for the vanadium battery prepared by the present invention is greatly improved, which can effectively reduce the contact resistance, and further improve the energy and voltage efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a preparation mechanism diagram of a catalytically modified graphite felt for a vanadium battery according to the present invention.

[0023] Figure 2 It is a scanning electron microscope image during the test process of Example 1 of the present invention; a is the acid-pretreated graphite felt, b is the polypyrrole-modified graphite felt, c is the carbon nanotube-modified graphite felt, and d is the catalytically modified graphite felt.

[0024] Figure 3 It is a scanning electron microscope image of the catalytically modified graphite felt of Example 1 and Comparative Example 1 of the present invention; a is the catalytically modified graphite felt of Example 1, and b is the catalytically modified graphite felt of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following description of at least one exemplary embodiment is merely illustrative and in no way restrictive of the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0026] See Figure 1 , the preparation principle of a catalytically modified graphite felt electrode for a vanadium battery in the present invention is as follows: First, the surface of the graphite felt fibers is functionalized to provide more reaction sites, and pyrrole monomers are grown on the graphite felt fibers by in-situ growth under the action of an initiator to obtain polypyrrole-modified graphite felt. Secondly, carboxyl carbon nanotubes and polypyrrole are connected by hydrogen bonds and π-π conjugate interactions. Finally, through the electrostatic interaction between the surfactant and the carbon nanotubes, polypyrrole particles are grown on the surface of the carbon nanotubes to achieve the preparation of the catalytically modified graphite felt.

[0027] Example 1: A method for preparing a catalytically modified graphite felt electrode for a vanadium battery, comprising the following steps: Step S1: Acid pretreatment of the graphite felt: Immerse the graphite felt in a concentrated sulfuric acid solution with a mass fraction of 98% at 25 °C for 10 h, wash with deionized water and vacuum dry to obtain the acid-pretreated graphite felt.

[0028] Step S2: Preparation of polypyrrole-modified graphite felt: Add 3 parts by mass of pyrrole monomers to a mixed solution of 100 parts by mass of deionized water and ethanol, the mass ratio of deionized water to ethanol is 50:1, then add 1 part by mass of the acid-pretreated graphite felt, and finally slowly add 10 parts by mass of a 2% mass fraction of ammonium persulfate initiator solution, turn on the circulation pump for circulation and dispersion, the reaction temperature is -2 °C, react for 18 h, and after the reaction, wash with water and ethanol and vacuum dry to obtain the polypyrrole-modified graphite felt.

[0029] Step S3: Preparation of carbon nanotube-modified graphite felt: Mix 1.5 parts by mass of carboxyl carbon nanotubes, 0.5 part by mass of polyvinylpyrrolidone and 100 parts by mass of deionized water, ultrasonically disperse for 1.5 h and then transfer to a reactor, then add the polypyrrole-modified graphite felt to the reactor, turn on the circulation pump for circulation and dispersion, blend at 70 °C for 3 h, place in a muffle furnace, heat up at a heating rate of 5 °C / min to 480 °C, and keep warm for 3 h for sintering to obtain the carbon nanotube-modified graphite felt.

[0030] Step S4: Preparation of catalytically modified graphite felt: Disperse 2 parts by mass of surfactant cetyl dimethyl ammonium chloride and 1 part by mass of pyrrole monomer in 100 parts by mass of deionized water, add carbon nanotube modified graphite felt, adjust the pH value to 5 with hydrochloric acid, drop 10 parts by mass of a 2% initiator ammonium persulfate solution into the reactor, turn on the circulation pump for circulating dispersion, the reaction temperature is 0 °C, react for 20 h, and after the reaction, wash with water and ethanol and then vacuum dry to obtain the catalytically modified graphite felt. As Figure 2 shown, in the figure, a is the acid-pretreated graphite felt, b is the polypyrrole-modified graphite felt, c is the carbon nanotube-modified graphite felt, d is the catalytically modified graphite felt. Polypyrrole grows in situ on the surface of the fiber in the polypyrrole-modified graphite felt, carbon nanotubes are further uniformly loaded on the fiber surface in the carbon nanotube-modified graphite felt, and polypyrrole particles are further loaded on the carbon nanotubes on the fiber surface in the catalytically modified graphite felt, indicating that the catalytically modified graphite felt is successfully prepared.

[0031] Example 2: A preparation method of a catalytically modified graphite felt electrode for a vanadium battery, comprising the following steps: Step S1: Acid pretreatment of graphite felt: Immerse the graphite felt in a 98% concentrated sulfuric acid solution at 30 °C for 9 h, wash with deionized water and vacuum dry to obtain the acid-pretreated graphite felt.

[0032] Step S2: Preparation of polypyrrole-modified graphite felt: Add 4 parts by mass of pyrrole monomer to a mixed solution of 100 parts by mass of deionized water and ethanol, the mass ratio of deionized water to ethanol is 40:1, then add 3 parts by mass of the acid-pretreated graphite felt, and finally slowly add 15 parts by mass of a 1.5% potassium persulfate initiator solution, turn on the circulation pump for circulating dispersion, the reaction temperature is 0 °C, react for 16 h, and after the reaction, wash with water and ethanol and vacuum dry to obtain the polypyrrole-modified graphite felt.

[0033] Step S3: Preparation of carbon nanotube-modified graphite felt 0: Blend and ultrasonically disperse 2 parts by mass of carboxyl carbon nanotubes, 1 part by mass of polyvinylpyrrolidone and 100 parts by mass of deionized water for 2 h and then transfer to a reactor, then add the polypyrrole-modified graphite felt to the reactor, turn on the circulation pump for circulating dispersion, blend at 80 °C for 2 h, place in a muffle furnace, heat up to 450 °C at a heating rate of 2 °C / min, and keep the temperature for 2 h for sintering to obtain the carbon nanotube-modified graphite felt.

[0034] Step S4: Preparation of catalytically modified graphite felt: Disperse 1 part by mass of surfactant dodecyldimethylamine oxide and 0.5 part by mass of pyrrole monomer in 100 parts by mass of deionized water, add carbon nanotube modified graphite felt, adjust the pH value to 4 with hydrochloric acid, drop 15 parts by mass of a 1.5% initiator potassium persulfate solution into the reactor, turn on the circulation pump for circulating dispersion, the reaction temperature is 3°C, react for 18 h, and after the reaction, wash with water and ethanol and then dry in vacuum to obtain the catalytically modified graphite felt.

[0035] Example 3: A preparation method of a catalytically modified graphite felt electrode for a vanadium battery, comprising the following steps: Step S1: Acid pretreatment of graphite felt: Immerse the graphite felt in a concentrated sulfuric acid solution with a mass fraction of 98% at 40°C for 9 h, wash with deionized water and dry in vacuum to obtain the acid-pretreated graphite felt.

[0036] Step S2: Preparation of polypyrrole-modified graphite felt: Add 5 parts by mass of pyrrole monomer to a mixed solution of 100 parts by mass of deionized water and ethanol, the mass ratio of deionized water to ethanol is 20:1, then add 2 parts by mass of acid-pretreated graphite felt, and finally slowly add 20 parts by mass of a 1% mass fraction of initiator sodium persulfate solution, turn on the circulation pump for circulating dispersion, the reaction temperature is -5°C, react for 20 h, and after the reaction, wash with water and ethanol and then dry in vacuum to obtain the polypyrrole-modified graphite felt.

[0037] Step S3: Preparation of carbon nanotube-modified graphite felt: Blend and ultrasonically disperse 1 part by mass of carboxyl carbon nanotubes, 0.8 part by mass of polyvinylpyrrolidone and 100 parts by mass of deionized water for 1 h and then transfer to a reactor, then add the polypyrrole-modified graphite felt to the reactor, turn on the circulation pump for circulating dispersion, blend at 60°C for 4 h, place in a muffle furnace, heat up to 500°C at a heating rate of 7°C / min, and keep warm for 4 h for sintering to obtain the carbon nanotube-modified graphite felt.

[0038] Step S4: Preparation of catalytically modified graphite felt: Disperse 1.5 parts by mass of surfactant octadecyltrimethylammonium chloride and 2 parts by mass of pyrrole monomer in 100 parts by mass of deionized water, add carbon nanotube modified graphite felt, adjust the pH value to 6 with hydrochloric acid, drop 20 parts by mass of a 1% initiator sodium persulfate solution into the reactor, turn on the circulation pump for circulating dispersion, the reaction temperature is 2°C, react for 22 h, and after the reaction, wash with water and ethanol and then dry in vacuum to obtain the catalytically modified graphite felt.

[0039] Example 4: A preparation method of a catalytically modified graphite felt electrode for a vanadium battery, comprising the following steps: Step S1: Acid pretreatment of graphite felt: Immerse the graphite felt in a concentrated sulfuric acid solution with a mass fraction of 98% at 35°C for 8 h, wash with deionized water and dry in vacuum to obtain the acid-pretreated graphite felt.

[0040] Step S2: Preparation of polypyrrole-modified graphite felt: Add 4 parts by mass of pyrrole monomer to a mixed solution of 100 parts by mass of deionized water and ethanol, where the mass ratio of deionized water to ethanol is 30:1. Then add 2 parts by mass of acid-pretreated graphite felt. Finally, slowly add 15 parts by mass of a 1.5% ammonium persulfate initiator solution. Turn on the circulation pump for circulation and dispersion. The reaction temperature is 3 °C, and the reaction lasts for 16 h. After the reaction, wash with water and ethanol and then dry under vacuum to obtain polypyrrole-modified graphite felt.

[0041] Step S3: Preparation of carbon nanotube-modified graphite felt: Blend 1.5 parts by mass of carboxyl carbon nanotubes, 0.5 part by mass of polyvinylpyrrolidone, and 100 parts by mass of deionized water, ultrasonically disperse for 1.5 h, and then transfer to a reactor. Then add the polypyrrole-modified graphite felt to the reactor, turn on the circulation pump for circulation and dispersion, and blend at 75 °C for 3 h. Place it in a muffle furnace, heat it at a heating rate of 10 °C / min to 470 °C, and keep it at this temperature for 3 h for sintering to obtain carbon nanotube-modified graphite felt.

[0042] Step S4: Preparation of catalytically modified graphite felt: Disperse 1.5 parts by mass of surfactant cetyl dimethyl ammonium chloride and 1.5 parts by mass of pyrrole monomer in 100 parts by mass of deionized water, add the carbon nanotube-modified graphite felt, adjust the pH value to 5.5 with hydrochloric acid, drop 15 parts by mass of a 1.5% ammonium persulfate initiator solution into the reactor, turn on the circulation pump for circulation and dispersion, the reaction temperature is 1 °C, and the reaction lasts for 24 h. After the reaction, wash with water and ethanol and then dry under vacuum to obtain catalytically modified graphite felt.

[0043] Comparative Example 1: Same as Example 1, without the preparation of polypyrrole-modified graphite felt in Step S2. In Step S3, use acid-pretreated graphite felt to load carbon nanotubes.

[0044] Comparative Example 2: Same as Example 1, without sintering in Step S3.

[0045] Comparative Example 3: Same as Example 1, without Step S4.

[0046] Comparative Example 4: Blank graphite felt.

[0047] The graphite felts prepared in Examples 1-4 and Comparative Examples 1-4 were cut into a size of 3 cm * 3 cm. Copper plates were placed at both ends, and a digital display pressure testing machine was used to keep the deformation of the graphite felt at 25%, and the stress was tested. A low-resistance tester was respectively clamped on the copper plates at both ends to test the resistance at a deformation of 25%. The graphite felts prepared in the examples and comparative examples were respectively assembled into a battery stack and subjected to charge and discharge tests under the same test conditions. The Coulomb efficiency, voltage efficiency, energy efficiency of the battery and the capacity retention rate after 100 cycles were recorded. The test results are shown in Table 1: Table 1 Summary of test results Index Stress (N) Resistance (mΩ) Coulombic efficiency Energy efficiency Voltage efficiency Capacity retention rate after 100 cycles Example 1 94.6 21.4 97.1% 91.6% 94.3% 98.6% Example 2 94.8 20.8 97.0% 91.8% 94.6% 98.4% Example 3 94.2 22.2 97.1% 91.2% 93.9% 98.5% Example 4 94.5 21.6 97.3% 91.5% 94.0% 98.6% Comparative example 1 94.0 22.4 97.1% 91.3% 94.0% 88.6% Comparative example 2 94.2 22.2 97.0% 87.3% 90.0% 98.5% Comparative example 3 94.6 21.5 97.2% 89.4% 92.0% 98.2% Comparative example 4 60.8 45.9 97.1% 85.1% 87.6% 98.1% As can be seen from Table 1, Examples 1-4 have a similar capacity retention rate compared to Comparative Example 4, indicating that the carbon nanomaterials loaded on the graphite felt fibers in Examples 1-10 do not affect their capacity retention rate performance, indicating that the carbon nanotubes in Examples 1-4 can be firmly loaded on the graphite felt fibers and are not easily washed away. Secondly, the capacity retention rate of Comparative Example 1 is slightly lower than that of Examples 1-4, which further illustrates the important role of polypyrrole in firmly loading carbon nanotubes. Finally, as Figure 3 can be seen from the scanning electron microscope images of Example 1 and Comparative Example 1, the carbon nanotube content in Example 1 is much higher than that in Comparative Example 1, further indicating that polypyrrole, as a conductive binder, binds carbon nanotubes to the graphite felt fibers through hydrogen bonding and π-π conjugation, and the carbon nanotubes are evenly loaded and have a high loading amount. Examples 1-4 and Comparative Examples 1-3 all have higher stress, lower resistance and higher battery efficiency, indicating that the catalytically modified graphite felt fibers for vanadium batteries prepared by the present invention have been greatly improved in strength, can effectively reduce the contact resistance, and thus can improve the energy and voltage efficiency of the battery. Examples 1-4 and Comparative Example 2 have higher energy and voltage efficiency because, through the sintering process of the present invention, part of the dispersant polyvinylpyrrolidone is carbonized, while maintaining the bonding force of the carbon nanotube-modified graphite felt, the conductivity is improved, and the energy and voltage efficiency of the battery are further increased. Examples 1-4 have higher energy and voltage efficiency compared to Comparative Example 3 because, in the catalytically modified graphite felt electrode prepared by the present invention, polypyrrole particles grow on the carbon nanotubes through the electrostatic interaction between the surfactant and carboxyl carbon nanotubes, increasing the reaction active area and active sites, providing faster ion transport and lower resistance, further enhancing the catalytic activity of the electrode, and further greatly improving the energy and voltage efficiency of the battery.

[0048] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a catalytically modified graphite felt electrode for a vanadium battery, characterized in that: It includes the following steps: Step S1: Acid pretreatment of graphite felt: Immerse the graphite felt in concentrated sulfuric acid solution with a mass fraction of 98%, wash it with deionized water, and then vacuum dry it to obtain acid-pretreated graphite felt; Step S2: Preparation of polypyrrole-modified graphite felt: Add 3-5 parts by mass of pyrrole monomer to a mixed solution of 100 parts by mass of deionized water and ethanol, then add 1-3 parts by mass of acid-pretreated graphite felt, and finally slowly add 10-20 parts by mass of initiator solution. Turn on the circulation pump for circulation and dispersion. After the reaction, wash it with water and ethanol and then vacuum dry it to obtain polypyrrole-modified graphite felt; Step S3: Preparation of carbon nanotube-modified graphite felt: Ultrasonically disperse 1-2 parts by mass of carboxyl carbon nanotubes, 0.5-1 part by mass of dispersant polyvinylpyrrolidone and 100 parts by mass of deionized water for 1-2 h, then transfer it to a reactor, add polypyrrole-modified graphite felt to the reactor, turn on the circulation pump for circulation and dispersion, blend and sinter to obtain carbon nanotube-modified graphite felt; Step S4: Preparation of catalytically modified graphite felt: Disperse 1-2 parts by mass of surfactant and 0.5-2 parts by mass of pyrrole monomer in 100 parts by mass of deionized water, add carbon nanotube-modified graphite felt, adjust the pH value with hydrochloric acid, drop 10-20 parts by mass of initiator solution into the reactor, turn on the circulation pump for circulation and dispersion. After the reaction, wash it with water and ethanol and then vacuum dry it to obtain catalytically modified graphite felt.

2. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In step S1, the soaking temperature is 25-40 °C and the soaking time is 8-10 h.

3. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In step S2, the mass ratio of deionized water to ethanol in the mixed solution is (20~50):

1.

4. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In step S2, the reaction temperature is -5-3 °C and the reaction time is 16-20 h.

5. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In steps S2 and S4, the initiator is at least one of ammonium persulfate, sodium persulfate and potassium persulfate, and the mass fraction of the initiator solution is 1-2%.

6. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: The blending temperature in step S3 is 60-80 °C and the blending time is 2-4 h.

7. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: The sintering method in step S3 is to place it in a muffle furnace, heat it at a heating rate of 2-10 °C / min to 450-500 °C, and keep it warm for 2-4 h.

8. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In step S4, the surfactant is at least one of cetyl dimethyl ammonium chloride, octadecyl trimethyl ammonium chloride and dodecyl dimethyl amine oxide.

9. The preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to claim 1, characterized in that: In step S4, the pH value is 4-6; the reaction temperature is 0-3 °C and the reaction time is 18-24 h.

10. A catalytically modified graphite felt electrode for a vanadium battery, characterized in that: The catalytically modified graphite felt electrode is obtained by the preparation method of a catalytically modified graphite felt electrode for a vanadium battery according to any one of claims 1-9.

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