Lead-bismuth alloy modified graphite felt, preparation method thereof, and application thereof in preparing iron-chromium liquid flow battery

Abstract

The present invention relates to a lead-bismuth alloy modified graphite felt, a preparation method thereof, and an application thereof in the preparation of an iron-chromium flow battery. The method comprises: (1) soaking raw graphite felt in concentrated sulfuric acid to obtain acid-treated graphite felt; (2) adding sodium pyrophosphate, L-tartaric acid, lead nitrate, and bismuth (III) nitrate pentahydrate to a nitric acid solution, and ultrasonically oscillating to obtain a lead-bismuth ion electrodeposition solution; (3) soaking the acid-treated graphite felt in the lead-bismuth ion electrodeposition solution, and ultrasonically oscillating to perform electrodeposition modification at a constant voltage to obtain a lead-bismuth alloy modified graphite felt. The present invention utilizes metallic bismuth and lead to perform electrodeposition modification on the graphite felt electrode. Bismuth can not only promote the redox reaction of chromium ions, but also enhance the reversibility of the reaction; lead can effectively inhibit the occurrence of hydrogen evolution reaction, thereby promoting the intensity of the redox reaction of the battery negative electrode and enhancing the reversibility of the reaction while inhibiting the occurrence of hydrogen evolution reaction, thereby improving the battery efficiency and lifespan.

Description

Technical Field

[0001] The invention relates to a lead-bismuth alloy modified graphite felt, a preparation method thereof and application thereof in preparing an iron-chromium liquid flow battery, and belongs to the technical field of electrochemical energy storage. Background Art

[0002] With the advancement of science and technology and industry, fossil fuels are increasingly questioned and rejected due to their inherent limitations and environmental pollution. Renewable energy, as an environmentally friendly and efficient new energy source, is gaining increasing attention. However, due to the intermittent and volatile nature of renewable energy, large-scale energy storage devices with sufficient stability and controllability are needed to achieve sustainable energy utilization. Flow batteries, with their advantages of high safety and stability, strong controllability, long cycle life, and environmental friendliness, are considered one of the preferred technologies for large-scale energy storage.

[0003] Liquid flow batteries are divided into positive and negative poles, separated by a semipermeable membrane in the middle. The positive and negative electrolytes are stored in external storage tanks, and circulate between the battery and the storage tank through the work of the pump in the working state. During the charge and discharge process, the electrolyte enters the battery from the storage tank, generates / consumes electrons on the surface of the electrode, and these electrons are transferred to the outside through the electrode, thus completing the conversion between chemical energy and electrical energy. According to the different substances that undergo redox reactions at the positive and negative electrodes, they can be divided into multiple categories. Among them, all-vanadium liquid flow batteries and iron-chromium liquid flow batteries are the most widely studied and applied due to their excellent performance. However, due to the high price of vanadium, all-vanadium liquid flow batteries are difficult to promote for commercial application, while iron-chromium liquid flow battery materials are relatively cheap and have unique commercial advantages. However, the Cr in the negative electrode of the iron-chromium liquid flow battery 3+ / Cr 2+ The redox reaction has poor reversibility, low activity and is prone to hydrogen evolution reaction, which is the primary problem restricting the development and application of this battery.

[0004] In order to solve the above problems, people have made great efforts in recent years, mainly in the development and improvement of electrolytes, membranes and electrodes. Among them, the electrode is one of the key materials of liquid flow batteries, and it is also the main place where electrochemical reactions occur, providing a channel for the transport of electrons. The polarization loss of the battery includes electrochemical polarization, ohmic polarization and concentration polarization. The above polarization losses determine the performance of the battery electrode and affect the Coulombic efficiency and current density of the liquid flow battery. The ideal electrode needs to have high electrochemical activity and reaction reversibility, enhance the electrode reaction rate to reduce electrochemical polarization loss, high conductivity to reduce ohmic polarization loss, high specific surface area, appropriate porosity, and increase the ion diffusion rate to reduce concentration polarization loss.

[0005] Doping metal atoms onto the electrode surface provides more active sites for electrode reactions, reduces electrode polarization, and enhances catalytic activity and stability, making it a mainstream method for electrode modification. Precious metals such as Pt and Au are commonly used in metal-modified electrodes, increasing battery costs and negating the inherent advantages of iron-chromium flow batteries. Using two or more metals to create alloys is one of the best ways to replace precious metals and reduce costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides a lead-bismuth alloy-modified graphite felt, its preparation method, and its application in the preparation of iron-chromium flow batteries. The present invention uses electrodeposition to dope a lead-bismuth alloy onto a graphite felt substrate to form a lead-bismuth alloy-modified graphite felt. This lead-bismuth alloy-modified graphite felt can be used as an electrode in an iron-chromium flow battery, enhancing the intensity of the redox reaction at the negative electrode and suppressing the hydrogen evolution reaction.

[0007] The technical solutions of the present invention are as follows:

[0008] A method for preparing lead-bismuth alloy modified graphite felt comprises the following steps:

[0009] (1) Acid treatment of graphite felt electrode: soak the original graphite felt in concentrated sulfuric acid, take it out, wash it and dry it to obtain acid-treated graphite felt;

[0010] (2) Preparation of a lead-bismuth ion electrodeposition solution: sodium pyrophosphate, L-tartaric acid, lead nitrate, and bismuth (III) nitrate pentahydrate are added to a nitric acid solution, followed by ultrasonic treatment to obtain a lead-bismuth ion electrodeposition solution;

[0011] (3) Electrodeposition modification of acid-treated graphite felt: The acid-treated graphite felt obtained in step (1) is immersed in the lead-bismuth ion electrodeposition solution obtained in step (2), subjected to ultrasonic oscillation, and then subjected to electrodeposition modification of the acid-treated graphite felt using a three-electrode system at a constant voltage. After the electrodeposition modification is completed, the graphite felt is cleaned and dried to obtain a lead-bismuth alloy-modified graphite felt.

[0012] According to the preferred embodiment of the present invention, in step (1), the concentration of the concentrated sulfuric acid is 98%, and the soaking time is 8 to 12 hours. The acid soaking can remove impurities on the surface of the graphite felt and etch it, thereby increasing the specific surface area and oxygen-containing functional groups of the graphite felt.

[0013] More preferably, the soaking time is 10 hours.

[0014] According to a preferred embodiment of the present invention, in step (1), the cleaning and drying are specifically as follows: first cleaning with deionized water for 3 times, and then drying at 100-120° C. for 0.5-1 h.

[0015] Preferably, according to the present invention, in step (2), the concentration of the nitric acid solution is 5 mol / L, and the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is (1-3): (1-3).

[0016] Further preferably, for a graphite felt having an area of ​​1.5*1.5 cm, the added amounts of the sodium pyrophosphate, L-tartaric acid, lead nitrate, and bismuth (III) nitrate pentahydrate are: 3 g sodium pyrophosphate, 0.161 g L-tartaric acid, 0.662 g lead nitrate, and 2.910 g bismuth (III) nitrate pentahydrate, respectively, and the volume of the nitric acid solution is 50 mL; the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is 1:3.

[0017] According to the preferred embodiment of the present invention, in step (2), the ultrasonic oscillation treatment time is 10 to 30 minutes.

[0018] According to the preferred embodiment of the present invention, in step (3), the ultrasonic oscillation treatment time is 5 to 15 minutes.

[0019] Preferably according to the present invention, in step (3), the constant voltage is -1 to -0.5V.

[0020] Further preferably, the constant voltage is -0.8V.

[0021] According to a preferred embodiment of the present invention, in step (3), the working electrode in the three-electrode system is an acid-treated graphite felt, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. Electrodeposition modification using the three-electrode system allows the lead-bismuth ions in the electrodeposition solution to be reduced on the surface of the graphite felt. Since metallic bismuth readily alloys with other metals, the lead-bismuth ions on the graphite felt surface are reduced to a lead-bismuth alloy.

[0022] Preferably according to the present invention, in step (3), the electrodeposition modification time is 30 to 100 seconds.

[0023] Further preferably, the electrodeposition modification time is 50s.

[0024] According to the preferred embodiment of the present invention, in step (3), the cleaning and drying are specifically as follows: first rinsing with anhydrous ethanol and deionized water three times in sequence, and then drying at 100-120° C. for 0.5-1 h.

[0025] A lead-bismuth alloy modified graphite felt is prepared according to the above method.

[0026] The above-mentioned lead-bismuth alloy modified graphite felt is used as an electrode of an iron-chromium liquid flow battery in the preparation of an iron-chromium liquid flow battery.

[0027] The technical features and beneficial effects of the present invention are as follows:

[0028] 1. This invention utilizes metallic bismuth and metallic lead to electrodeposit graphite felt electrodes. Bismuth not only promotes the redox reaction of chromium ions but also significantly enhances the reversibility of the reaction. Lead effectively inhibits the hydrogen evolution reaction. Therefore, the lead-bismuth alloy-modified graphite felt provided by this invention can be used as an electrode in iron-chromium flow batteries. While promoting the intensity and reversibility of the redox reaction at the battery's negative electrode, it can also inhibit the hydrogen evolution reaction, thereby reducing polarization losses and improving battery efficiency and lifespan.

[0029] 2. Compared with the existing modification method of reducing metal oxides to metals through electrochemical deoxidation, the preparation method of lead-bismuth alloy-modified graphite felt provided by the present invention is simpler in production process and has higher operational safety. Moreover, the electro-deoxidation method simply reduces bimetallic oxides to bimetallics, while the electro-reduction method can reduce bimetallic ions to metal alloys with more stable structural properties.

[0030] 3. The lead-bismuth alloy-modified graphite felt prepared in this invention can provide more active reaction sites for the negative electrode redox reaction, enhancing the reaction intensity and reversibility, reducing polarization losses, and improving the electrode electrochemical performance. It can also increase the potential for the negative electrode hydrogen evolution reaction, thereby inhibiting the hydrogen evolution reaction and improving battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the SEM morphology of the lead-bismuth alloy modified graphite felt prepared in Example 1 of the present invention.

[0032] Figure 2 This is the mapping result of the lead-bismuth alloy modified graphite felt prepared in Example 1 of the present invention.

[0033] Figure 3 1 is a cyclic voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 1 of the present invention.

[0034] Figure 4 1 is a cyclic voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 2 of the present invention.

[0035] Figure 5 3 is a cyclic voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 3 of the present invention.

[0036] Figure 6 3 is a slow linear sweep voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 1 of the present invention.

[0037] Figure 7 3 is a slow linear sweep voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 2 of the present invention.

[0038] Figure 8 3 is a slow linear sweep voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 3 of the present invention.

[0039] Figure 9 1 is the electrochemical impedance spectroscopy diagram of the lead-bismuth alloy modified graphite felt prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0041] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0042] Example 1

[0043] A method for preparing lead-bismuth alloy modified graphite felt comprises the following steps:

[0044] (1) Acid treatment of graphite felt electrode: 1.5*1.5cm original graphite felt was soaked in 98% concentrated sulfuric acid solution for 10h, then washed with deionized water three times, and dried in a drying oven at 120°C for 1h to obtain acid-treated graphite felt; (2) Preparation of metal alloy electrodeposition solution: 3g sodium pyrophosphate, 0.161g L-tartaric acid, 0.662g lead nitrate, and 2.910g bismuth (III) nitrate pentahydrate were added to 50mL of 5mol / L nitric acid solution, and then ultrasonically shaken for 10min to fully dissolve the solid powder to obtain lead-bismuth ion electrodeposition solution;

[0045] Wherein, the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is 1:3;

[0046] (3) Electrodeposition modification of acid-treated graphite felt: The acid-treated graphite felt obtained in step (1) was immersed in the lead-bismuth ion electrodeposition solution obtained in step (2), and subjected to ultrasonic vibration treatment for 5 minutes. Then, the acid-treated graphite felt was subjected to electrodeposition modification using a three-electrode system at a constant voltage of -0.8 V. After electrodeposition modification for 50 seconds, the graphite felt was taken out and rinsed three times with anhydrous ethanol and deionized water in sequence. Finally, the graphite felt was dried in a drying oven at 120° C. for 1 hour to obtain a lead-bismuth alloy-modified graphite felt.

[0047] In the three-electrode system, the working electrode is acid-treated graphite felt, the counter electrode is a platinum sheet electrode, and the reference electrode is a saturated calomel electrode.

[0048] The microstructure of the lead-bismuth alloy modified graphite felt obtained in this embodiment is as follows: Figure 1 The specific material composition is as shown in Figure 2 shown.

[0049] Depend on Figure 1 It can be seen that the surface of the lead-bismuth alloy modified graphite felt carbon fiber of the present invention is grooved, which is due to the etching effect of sulfuric acid, which increases the specific surface area of ​​the graphite felt and enhances its hydrophilicity; the sediment is deposited in blocks and evenly deposited on the surface of the graphite felt carbon fiber.

[0050] Depend on Figure 2 It can be seen that the blocky deposits on the surface of the lead-bismuth alloy graphite felt fiber of the present invention are lead-bismuth elements, and the positions of the lead-bismuth elements are highly overlapped, which proves that the blocky deposits are lead-bismuth alloy.

[0051] Example 2

[0052] A method for preparing lead-bismuth alloy modified graphite felt comprises the following steps:

[0053] (1) Acid treatment of graphite felt electrode: 1.5*1.5cm original graphite felt was soaked in 98% concentrated sulfuric acid solution for 10h, then washed with deionized water three times, and dried in a drying oven at 120°C for 1h to obtain acid-treated graphite felt; (2) Preparation of lead-bismuth ion electrodeposition solution: 3g sodium pyrophosphate, 0.161g L-tartaric acid, 1.325g lead nitrate, and 1.940g bismuth (III) nitrate pentahydrate were added to 50mL of 5mol / L nitric acid solution, and then ultrasonically shaken for 10min to fully dissolve the solid powder to obtain lead-bismuth ion electrodeposition solution;

[0054] Wherein, the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is 1:1;

[0055] (3) Electrodeposition modification of acid-treated graphite felt: The acid-treated graphite felt obtained in step (1) was immersed in the lead-bismuth ion electrodeposition solution obtained in step (2), and subjected to ultrasonic vibration treatment for 5 minutes. Then, the acid-treated graphite felt was subjected to electrodeposition modification using a three-electrode system at a constant voltage of -0.8 V. After electrodeposition modification for 50 seconds, the graphite felt was taken out and rinsed three times with anhydrous ethanol and deionized water in sequence. Finally, the graphite felt was dried in a drying oven at 120° C. for 1 hour to obtain a lead-bismuth alloy-modified graphite felt.

[0056] In the three-electrode system, the working electrode is acid-treated graphite felt, the counter electrode is a platinum sheet electrode, and the reference electrode is a saturated calomel electrode.

[0057] Example 3

[0058] A method for preparing lead-bismuth alloy modified graphite felt comprises the following steps:

[0059] (1) Acid treatment of graphite felt electrodes: 1.5*1.5 cm original graphite felt was soaked in 98% concentrated sulfuric acid solution for 10 h, then washed three times with deionized water, and dried in a drying oven at 120°C for 1 h to obtain acid-treated graphite felt;

[0060] (2) Preparation of lead-bismuth ion electrodeposition solution: add 3g of sodium pyrophosphate,

[0061] 0.161 g of L-tartaric acid, 1.987 g of lead nitrate, and 0.970 g of bismuth (III) nitrate pentahydrate were added, followed by ultrasonic shaking for 10 minutes to fully dissolve the solid powder to obtain a lead-bismuth ion electrodeposition solution;

[0062] Wherein, the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is 3:1;

[0063] (3) Electrodeposition modification of acid-treated graphite felt: The acid-treated graphite felt obtained in step (1) was immersed in the metal alloy electrodeposition solution obtained in step (2), and subjected to ultrasonic vibration treatment for 5 minutes. Then, the acid-treated graphite felt was subjected to electrodeposition modification using a three-electrode system at a constant voltage of -0.8 V. After electrodeposition modification for 50 seconds, the graphite felt was taken out and rinsed three times with anhydrous ethanol and deionized water in sequence. Finally, the graphite felt was dried in a drying oven at 120° C. for 1 hour to obtain a lead-bismuth alloy-modified graphite felt.

[0064] In the three-electrode system, the working electrode is acid-treated graphite felt, the counter electrode is a platinum sheet electrode, and the reference electrode is a saturated calomel electrode.

[0065] Comparative Example 1

[0066] An acid-treated graphite felt is prepared according to the method described in step (1) of Example 1.

[0067] Test Example 1

[0068] 1. Cyclic voltammetry tests were performed on the lead-bismuth alloy-modified graphite felt prepared in Example 1 and the acid-treated graphite felt in Comparative Example 1. Specifically, the tests were performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 1, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was a mixed solution of 1 mol / L FeCl3 + 1 mol / L CrCl2 + 3 mol / L HCl.

[0069] The cyclic voltammetry curves of the lead-bismuth alloy modified graphite felt prepared in Example 1 and the acid-treated graphite felt in Comparative Example 1 are as follows: Figure 3 shown.

[0070] Depend on Figure 3It can be seen that the graphite felt treated only by acidification exhibits poor reversibility and no reduction peak appears; while the lead-bismuth alloy modified graphite felt not only has better reversibility performance, but also the intensity of the redox peak potential is enhanced.

[0071] 2. Cyclic voltammetry was performed on the lead-bismuth alloy-modified graphite felt prepared in Example 2. Specifically, the test was performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 2, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was a mixed solution of 1 mol / L FeCl3 + 1 mol / L CrCl2 + 3 mol / L HCl.

[0072] Example 2 The cyclic voltammetry curve of lead-bismuth alloy modified graphite felt is as follows Figure 4 shown.

[0073] 3. Cyclic voltammetry was performed on the lead-bismuth alloy-modified graphite felt prepared in Example 3. Specifically, the test was performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 3, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was a mixed solution of 1 mol / L FeCl3, 1 mol / L CrCl2, and 3 mol / L HCl.

[0074] Example 3 The cyclic voltammetry curve of lead-bismuth alloy modified graphite felt is as follows Figure 5 shown.

[0075] pass Figures 3-5 By comparison, it can be concluded that the redox reaction of the lead-bismuth alloy modified graphite felt in Example 1 occurs first, and the reduction reaction intensity is the strongest. Figures 3-5 The data are shown in Table 1 below.

[0076] Table 1

[0077]

[0078]

[0079] As shown in Table 1, from the perspective of reversibility, although the ΔE value of the lead-bismuth alloy modified graphite felt in Example 1 is not the lowest, its (I pa / I pc -1) is significantly lower than that of the other two samples, and still shows the best reversibility. Therefore, in general, the redox reaction efficiency of the lead-bismuth alloy modified graphite felt at the negative electrode in Example 1 is the highest.

[0080] Test Example 2

[0081] 1. Slow linear sweep voltammetry was performed on the lead-bismuth alloy-modified graphite felt prepared in Example 1 and the acid-treated graphite felt in Comparative Example 1. The specific test was carried out in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 1, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was HCl with a concentration of 3 mol / L.

[0082] The slow linear sweep voltammetry curves of the lead-bismuth alloy modified graphite felt prepared in Example 1 and the acid-treated graphite felt in Comparative Example 1 are as follows: Figure 6 shown.

[0083] Depend on Figure 6 It can be seen that the hydrogen evolution reaction of the graphite felt treated only by acidification is the most rapid and intense, and the hydrogen evolution reaction has occurred at the potential at the beginning of the scan. The hydrogen evolution reaction of the lead-bismuth alloy modified graphite felt is significantly inhibited, and the hydrogen evolution potential is increased.

[0084] 2. Slow linear sweep voltammetry was performed on the lead-bismuth alloy-modified graphite felt prepared in Example 2. Specifically, the test was performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 2, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was HCl with a concentration of 3 mol / L.

[0085] The slow linear sweep voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 2 is as follows: Figure 7 shown.

[0086] 3. Slow linear sweep voltammetry was performed on the lead-bismuth alloy-modified graphite felt prepared in Example 3. Specifically, the test was performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 3, a Pt sheet, and saturated calomel as the working electrode, counter electrode, and reference electrode, respectively. The electrolyte solution was HCl with a concentration of 3 mol / L.

[0087] The slow linear sweep voltammetry curve of the lead-bismuth alloy modified graphite felt prepared in Example 3 is as follows: Figure 8 shown.

[0088] pass Figures 6-8 By comparison, it can be concluded that the potentials of the three lead-bismuth alloy modified graphite felts for hydrogen evolution reaction are similar. 2 When the overpotential of the lead-bismuth alloy modified graphite felt of Example 1, Example 2, and Example 3 for hydrogen evolution reaction is -0.58 V, -0.58 V, and -0.54 V, respectively. The inhibitory effect of the lead-bismuth alloy modified graphite felt of Example 1 on the hydrogen evolution reaction is not much different from that of the other samples.

[0089] Test Example 3

[0090] Electrochemical impedance spectroscopy tests were performed on the lead-bismuth alloy-modified graphite felt and the original graphite felt prepared in Example 1. Specifically, the tests were performed in a three-electrode electrolytic cell consisting of the lead-bismuth alloy-modified graphite felt in Example 1, a Pt sheet, and a saturated calomel as the working electrode, the counter electrode, and the reference electrode, respectively. The electrolyte solution was a mixed solution of 1 mol / L FeCl3 + 1 mol / L CrCl2 + 3 mol / L HCl.

[0091] The electrochemical impedance spectroscopy of the lead-bismuth alloy modified graphite felt and the original graphite felt prepared in Example 1 is as follows: Figure 9 shown.

[0092] Depend on Figure 9 It can be seen that compared with the original graphite felt, the total impedance of the lead-bismuth alloy modified graphite felt in Example 1 is significantly smaller than that of the original graphite felt, the polarization loss is significantly reduced, and the dynamic performance is better.

[0093] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, to the extent such modifications and variations fall within the scope of the claims and their equivalents, the present invention is intended to encompass such modifications and variations. While the present invention has been described above through the use of embodiments, those skilled in the art will appreciate that any improvements and variations made to the present invention without departing from the spirit and substance of the present invention are intended to fall within the scope of the present invention.

Claims

1. A method for preparing lead-bismuth alloy modified graphite felt, characterized in that: The following steps are involved: (1) Acid treatment of graphite felt electrode: soak the original graphite felt in concentrated sulfuric acid, take it out, wash it and dry it to obtain acid-treated graphite felt; (2) Preparation of lead-bismuth ion electrodeposition solution: sodium pyrophosphate, L-tartaric acid, lead nitrate, and bismuth nitrate pentahydrate are added to a nitric acid solution, followed by ultrasonic treatment to obtain a lead-bismuth ion electrodeposition solution; (3) Electrodeposition modification of acid-treated graphite felt: The acid-treated graphite felt obtained in step (1) is immersed in the lead-bismuth ion electrodeposition solution obtained in step (2), subjected to ultrasonic oscillation, and then subjected to electrodeposition modification of the acid-treated graphite felt using a three-electrode system at a constant voltage. After the electrodeposition modification is completed, the graphite felt is cleaned and dried to obtain a lead-bismuth alloy-modified graphite felt.

2. The preparation method according to claim 1, wherein In step (1), the concentration of the concentrated sulfuric acid is 98%, and the soaking time is 8 to 12 hours.

3. The preparation method according to claim 2, wherein The soaking time is 10 hours.

4. The preparation method according to claim 1, wherein In step (1) and step (3), the cleaning and drying are specifically as follows: first, cleaning with deionized water for 3 times, and then drying at 100-120° C. for 0.5-1 h.

5. The preparation method according to claim 1, wherein In step (2), the concentration of the nitric acid solution is 5 mol / L, and the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is (1-3): (1-3).

6. The preparation method according to claim 1, wherein For a 1.5*1.5 cm graphite felt, the added amounts of sodium pyrophosphate, L-tartaric acid, lead nitrate, and bismuth nitrate pentahydrate are: 3 g of sodium pyrophosphate, 0.161 g of L-tartaric acid, 0.662 g of lead nitrate, and 2.910 g of bismuth nitrate pentahydrate, respectively; the volume of the nitric acid solution is 50 mL; and the molar ratio of lead ions to bismuth ions in the lead-bismuth ion electrodeposition solution is 1:

3.

7. The preparation method according to claim 1, wherein In step (3), the constant voltage is -1~-0.5V.

8. The preparation method according to claim 7, wherein The constant voltage is -0.8V.

9. The preparation method according to claim 1, wherein In step (3), the working electrode in the three-electrode system is an acid-treated graphite felt, the counter electrode is a platinum sheet electrode, and the reference electrode is a saturated calomel electrode.

10. The preparation method according to claim 1, wherein In step (3), the electrodeposition modification time is 30~100s.

11. The preparation method according to claim 10, characterized in that The electrodeposition modification time was 50 s.

12. A lead-bismuth alloy modified graphite felt, characterized in that: Prepared according to the method according to any one of claims 1 to 8.

13. Use of the lead-bismuth alloy modified graphite felt according to claim 12 as an electrode for an iron-chromium redox flow battery in the preparation of an iron-chromium redox flow battery.

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