Method for preparing graphene conductive polymer coating on surface of bipolar plate by electrodeposition method

Abstract

The present invention provides a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, comprising the following steps: Step 1, chemically modify graphene oxide to graft anionic functional groups to prepare a modified graphene oxide aqueous dispersion; Step 2, mix the modified graphene oxide aqueous dispersion and the conductive polymer monomer aqueous dispersion in a certain proportion to obtain an electrolyte; Step 3, pretreat the metal-based bipolar plate by immersing the metal-based bipolar plate in a sulfuric acid solution to remove the passivation film on its surface; Step 4, use the metal-based bipolar plate as the anode and a platinum sheet as the cathode, and perform electrodeposition on the metal-based bipolar plate with a DC power supply; Step 5, dry the deposited wet film to obtain a graphene conductive polymer composite coating. The present invention utilizes the doping effect of the functional groups on the surface of anionic modified graphene on the conductive polymer, promotes the π-electron delocalization of the conductive polymer, and improves the conductivity of the composite coating.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene coating, and the field of metal-based bipolar plate materials for proton exchange membrane fuel cells, and particularly relates to a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) have received attention due to their great potential in the zero-pollution transformation of energy problems. Bipolar plates (BPs) account for 60%–80% of the total mass of fuel cells, 70%–80% of the total volume, and 30%–45% of the total cost. They are an important material in PEMFCs, and their main functions in fuel cells include: 1. evenly distributing reaction gases in the active area through the gas flow channels on the plate; 2. providing mechanical support for the membrane electrode assembly; 3. transferring current between battery components; 4. removing water generated at the cathode; 5. preventing leakage of reaction gases; 6. removing heat generated by gas reactions; Therefore, bipolar plates need to withstand working environments such as high humidity, high potential, and high temperature (operating temperature 80°C). The performance indicators of bipolar plates set by the US Department of Energy in 2020 are: 1. corrosion current density (Icorr) < 1 μA / cm 2 ; 2. contact resistance (ICR) < 10 mΩ / cm 2 ; 3. conductivity > 100 S / cm; 4. thermal conductivity > 10 W / m٠K; 5. gas permeability < 2×10–6 cm 3 / s٠cm 2 ; 6. flexural strength > 50 MPa; 7. Shore hardness > 40.

[0003] Due to their excellent electrical and thermal conductivity, mechanical properties, gas tightness, machinability, and low cost, metal-based bipolar plates have become the main development trend of bipolar plate materials. However, metal bipolar plates are extremely prone to corrosion in the high-temperature, high-humidity, and high-potential working environments of fuel cells, forming a passivation film, increasing the contact resistance between the bipolar plate and the membrane electrode, and reducing the working efficiency of the fuel cell. Therefore, preparing a conductive and corrosion-resistant coating on the surface of metal-based bipolar plates is the key to realizing their application.

[0004] Coating materials commonly used on the surface of metal-based bipolar plates include three major categories: carbon materials, noble metals, and cermets. These coatings are usually deposited on metal substrates by methods such as chemical vapor deposition or physical vapor deposition, which are expensive, energy-consuming, and have low production efficiency. In addition, the standard electrode potentials of carbon materials and noble metals are usually higher than those of metal substrates. Once the electrolyte penetrates the interface between the coating and the substrate, the coating becomes the cathode and the metal substrate becomes the anode, which may lead to the accelerated corrosion of the substrate metal. The electrodeposition method proposed in the present invention is more efficient, more suitable for industrial production, and the composite coating of modified graphene and conductive polymer has both conductive performance, barrier performance, and corrosion inhibition performance, which can meet the requirements of PEMFC bipolar plates.

[0005] Due to the simple preparation method, easy film formation, low pollution, good anti-corrosion performance, and high conductivity, conductive polymers have been applied to the surface of metal-based bipolar plates. Its main corrosion protection mechanisms include: 1. Barrier effect 2. Anodic protection effect 3. Corrosion inhibition effect. However, the coating microdefects formed during the synthesis of a single conductive polymer coating will still cause the penetration of the electrolyte, making it difficult to withstand the harsh working environment of PEMFC. Therefore, it is crucial to improve the structural defects of the conductive polymer coating and increase its density. Summary of the Invention

[0006] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, for preparing a modified graphene conductive polymer composite coating with low contact resistance and high corrosion resistance, and this coating is used on the surface of the metal-based bipolar electrode in a proton exchange membrane fuel cell.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, including the following steps:

[0009] Including the following steps:

[0010] Step 1: Chemically modify graphene oxide, graft anionic functional groups, and prepare a modified graphene oxide aqueous dispersion;

[0011] Step 2: Mix the modified graphene aqueous dispersion and the conductive polymer monomer aqueous dispersion in a certain proportion to obtain an electrolyte;

[0012] Step 3: Pretreat the metal-based bipolar plate, soak the metal-based bipolar plate in a sulfuric acid solution to remove the passivation film on its surface;

[0013] Step 4: Use the metal-based bipolar plate as the anode and a platinum sheet as the cathode, and perform electrodeposition on the metal-based bipolar plate with a constant voltage DC power supply;

[0014] Step 5. Dry the obtained wet film by deposition to obtain a graphene conductive polymer composite coating.

[0015] As a preferred technical solution, in the said Step 1, the anionic functional groups include benzenesulfonic acid groups, sulfuric acid groups, and phosphoric acid groups.

[0016] As a preferred technical solution, in the said Step 2, the conductive polymer monomers include pyrrole, aniline, or thiophene.

[0017] As a preferred technical solution, in the said Step 2, the electrolyte further includes an initiator, a dispersion aid, and a surfactant.

[0018] As a preferred technical solution, in the said Step 2, the concentration of the modified graphene aqueous dispersion is 1 mg / ml - 4 mg / ml, and the concentration of the conductive polymer monomer is 0.01 mol / L - 0.15 mol / L.

[0019] As a preferred technical solution, in the said Step 3, the metal-based bipolar plate is a stainless steel bipolar plate or a titanium alloy bipolar plate. Use sandpaper to polish the surface of the metal-based bipolar plate to remove the surface passivation film, use acetone to remove the oil stains and fingerprints on the surface of the metal-based bipolar plate, and use ethanol to remove the excess solvent.

[0020] As a preferred technical solution, in the said Step 4, the deposition voltage is 1 - 5 V, and the deposition time is 10 - 20 min.

[0021] As a preferred technical solution, in the said Step 5, the wet film is dried by heating, and the temperature range is 40 - 80 °C.

[0022] As a preferred technical solution, place the obtained wet film by deposition in a vacuum oven, dry it at a constant temperature of 40 °C for 3 h. After the film layer on the sample surface is dried, change to drying at 80 °C for 10 h.

[0023] As a preferred technical solution, the anionic functional group of the modified graphene oxide is a benzenesulfonic acid group. The preparation method of the sulfonated graphene aqueous dispersion specifically includes the following steps:

[0024] Step a. Mix the graphene oxide aqueous dispersion (1 mg / ml) with the sodium borohydride solution (1.05 mol / L), and stir in a water bath at 80 °C to obtain a pre-reduced graphene oxide dispersion;

[0025] Step b. Mix aminobenzenesulfonic acid and sodium nitrite in an acidic environment and under ice bath conditions to obtain a diazonium salt solution;

[0026] Step c: Add the freshly prepared diazonium salt solution to the pre-reduced graphene oxide dispersion, and stir under ice bath conditions for 3 - 5 h;

[0027] Step d: Centrifuge and wash the mixture obtained in step c multiple times to remove excess reactants, and obtain a sulfonated graphene aqueous dispersion with a configured concentration of 1 - 4 mg / ml.

[0028] As a preferred technical solution, the anionic functional group of the modified graphene oxide is a phosphate group. The preparation of the phosphorylated graphene aqueous dispersion includes the following steps:

[0029] Step a: Slowly drip sodium hydroxide into hydroxyethylidene diphosphonic acid (60%) until the pH value equals 9 - 10;

[0030] Step b: Mix the graphene oxide aqueous dispersion (1 mg / ml) with the solution obtained in step a, and stir in a water bath at 80°C for 7 hours;

[0031] Step c: Centrifuge and wash the mixture obtained in step b multiple times to remove excess reactants, and obtain a phosphorylated graphene aqueous dispersion.

[0032] In the present invention, the modified graphene plays three roles: a. Physical barrier effect; b. As a template for the deposition of conductive polymers, making the morphology of the composite coating more flat and dense; c. The functional groups on the surface of the modified graphene play a doping role in the conductive polymer, promoting the π - electron delocalization of the conductive polymer.

[0033] The anionic functional groups on the surface of the modified graphene undergo "self - assembly" between the negative charges generated by the hydrolysis of the functional groups on the surface of the modified graphene and the conductive polymer reaching the oxidation potential; move towards the substrate under the action of the electric field force and align parallel to the surface of the metal substrate; in addition, the modified graphene has a two - dimensional shape and a large specific surface area, and can be used as a template for the growth of conductive polymers. The functional groups on the surface of the modified graphene can also perform anionic doping on the conductive polymer to promote its π - electron delocalization. Under the combined action of highly oriented modified graphene sheets, flat and dense composite coatings, and highly doped conductive polymers, a modified graphene conductive polymer composite coating with high conductivity and high corrosion resistance can be obtained. After depositing it on the surface of the metal - based bipolar plate, both the corrosion resistance and the interfacial contact resistance meet the performance requirements of the bipolar plate of the proton exchange membrane fuel cell.

[0034] As described above, the present invention has the following beneficial effects:

[0035] (1) Under the action of the electric field force, parallel arrangement of the two - dimensional sheets of the modified graphene on the surface of the metal - based bipolar plate is obtained, thereby improving the physical barrier performance of the composite coating.

[0036] (2) During the electrodeposition process of the conductive polymer material, using the modified graphene two-dimensional sheet as a template makes the morphology of the composite coating smoother and denser.

[0037] (3) The present invention utilizes the doping effect of the functional groups on the surface of anionic modified graphene on the conductive polymer, promotes the π-electron delocalization of the conductive polymer, and improves the conductivity of the composite coating.

[0038] (4) The electrodeposition method proposed by the present invention has lower energy consumption and significant advantages in production efficiency compared with physical vapor deposition and chemical vapor deposition, and is more suitable for industrialization requirements.

[0039] (5) The solvent used in the electrolyte of the present invention is mainly water, and the production process is green and environmentally friendly. Description of the Drawings

[0040] Figure 1 It shows the morphology of the modified graphene polypyrrole composite coating under a scanning electron microscope.

[0041] Figure 2 It shows the measurement results of the interfacial contact resistance of the modified graphene polypyrrole composite coating, the sulfuric acid-doped polypyrrole coating, and the graphene oxide polypyrrole composite coating.

[0042] Figure 3 It shows the potentiodynamic polarization test results of the modified graphene polypyrrole composite coating, the sulfuric acid-doped polypyrrole coating, and the graphene oxide polypyrrole composite coating. Detailed Embodiments

[0043] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Example 1

[0044] This example provides a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, including the following steps:

[0045] Step 1. Prepare modified graphene;

[0046] Step 1.1. Disperse 1 g of graphene oxide in 1 L of water, stir to mix evenly, and then stir and disperse the graphene oxide dispersion at a speed of 600 rpm to obtain a 1 mg / mL graphene oxide dispersion that is well dispersed in an aqueous solution;

[0047] Step 1.2: Adjust the pH of the dispersion to alkaline (pH = 9 - 10) using sodium hydroxide. Prepare an aqueous solution of sodium borohydride (1.05 mol / L), mix the prepared aqueous solution of sodium borohydride with the dispersion, stir at 80 °C, perform a pre-reduction treatment on the graphene oxide dispersion, and centrifuge the pre-reduced graphene oxide.

[0048] Step 1.3: Perform sulfonation modification on the pre-reduced graphene oxide.

[0049] The specific steps of Step 1.3 are as follows:

[0050] Step a: Add 0.65 g of sulfanilic acid and 0.24 g of sodium nitrite to an aqueous hydrochloric acid solution with pH = 3 under an ice bath condition at 0 °C, mix and react for 1 h to obtain a diazonium salt solution.

[0051] Step b: Add the diazonium salt solution obtained in Step a to the aqueous dispersion of pre-reduced graphene oxide, and continuously stir and react for 4 h under an ice bath condition at 0 °C to obtain a sulfonated graphene dispersion.

[0052] Step c: Centrifuge the sulfonated graphene dispersion obtained in Step b at a speed of 20000 rpm, wash the obtained solid with deionized water to remove excess reactants, obtain sulfonated graphene, and disperse the obtained sulfonated graphene in water.

[0053] Step Two: Prepare a graphene conductive polymer coating;

[0054] The metal-based bipolar plate material is SS304. Use sandpaper (200 mesh and 1000 mesh) to polish the stainless steel surface to remove the surface passivation film; use acetone to remove surface oil stains and fingerprints, use ethanol to remove excess solvent, and put the polished sample into 1 mol / L H2SO4 to further remove the surface passivation film and increase the surface binding sites.

[0055] Step 2.2: Prepare a 3 mg / ml aqueous solution of sulfonated graphene, add pyrrole (0.05 mol / L) to obtain a mixed electrolyte solution, stir the mixed solution at 600 rmp for 10 min, and ultrasonicate at 150 Hz for 10 min (the ultrasonic temperature is 24 °C) to obtain a uniformly mixed electrolyte solution.

[0056] Step 2.3: Install the polished and cleaned SS304 on the electrode clamp and use it as the working electrode, and use a platinum sheet as the counter electrode; perform electrodeposition on the sample using a constant voltage DC power supply, with a deposition voltage of 1.2 V and a deposition time of 10 min.

[0057] Step 2.4: Place the deposited wet film in a vacuum oven and dry it at a constant temperature of 40 °C for 3 h. After the film layer on the sample surface is dried, switch to drying at 80 °C for 10 h.

[0058] Step 2.5: Characterize the metal-based bipolar plate containing modified graphene. The electron microscope photo shows that the thickness of the prepared graphene coating is about 9 μm, as Figure 1 shown. The contact resistance of the bipolar plate is 5 mΩ•cm 2 (the contact resistance test condition is 1.5 MPa), and the electrochemical test result shows that the corrosion current is 0.5 μA / cm 2 (the potentiodynamic polarization test condition is H2SO4 solution with PH = 3 at 80 °C). It shows that both the corrosion resistance and the contact resistance of the graphene conductive polymer composite coating prepared by this method meet the requirements of the bipolar plate of the proton exchange membrane fuel cell. Example 2

[0059] This example provides a method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, including the following steps:

[0060] Step 1: The metal-based bipolar plate material is SS304. Use sandpaper (200 mesh and 1000 mesh) to polish the stainless steel surface to remove the surface passivation film; use acetone to remove surface oil stains and fingerprints, use ethanol to remove the excess solvent, and put the polished sample into 1 mol / L H2SO4 to further remove the surface passivation film and increase the surface binding sites;

[0061] Step 2: Prepare a 1 mg / ml aqueous solution of sulfonated graphene, add pyrrole (0.05 mol / L) to obtain a mixed electrolyte solution, stir the mixed solution at a speed of 600 rmp for 10 min, and ultrasonicate it at 150 Hz for 10 min (the ultrasonic temperature is 24 °C) to obtain a uniformly mixed electrolyte solution;

[0062] Step 3: Install the polished and cleaned SS304 on the electrode clamp and use it as the working electrode, and use a platinum sheet as the counter electrode; use a constant voltage DC power supply to perform electrodeposition on the sample, with a deposition voltage of 5 V and a deposition time of 20 min;

[0063] Step 4: Place the deposited wet film in a vacuum oven and dry it at a constant temperature of 40 °C for 3 h. After the film layer on the sample surface is dried, change to 80 °C and dry it for 10 h;

[0064] Step 5: Characterize the metal-based bipolar plate containing modified graphene. The contact resistance of the bipolar plate is 16 mΩ•cm 2 (the test condition is under 1.4 MPa), and the electrochemical test result shows that the corrosion current is 18.729 μA / cm 2(The potentiodynamic polarization test was carried out in a H2SO4 solution with a pH of 3 at 80 °C). The test results show that changing the proportion of modified graphene in the electrolyte will affect the contact resistance and corrosion resistance of the metal-based bipolar plate. By increasing the concentration of benzenesulfonic acid groups in the electrolyte, the contact resistance of the composite coating can be effectively reduced.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a sulfuric acid-doped conductive polymer coating, which includes the following steps:

[0067] Step 1: The metal-based bipolar plate material is SS304. The surface of the stainless steel is polished with sandpaper (200 mesh and 1000 mesh) to remove the surface passivation film; acetone is used to remove surface oil stains and fingerprints, and ethanol is used to remove excess solvent. The polished sample is placed in 1 mol / L H2SO4 to further remove the surface passivation film and increase the surface binding sites;

[0068] Step 2: Prepare a 0.5 mol / L H2SO4 aqueous solution, add pyrrole (0.05 mol / L) to obtain a mixed electrolyte, stir the mixed solution at a speed of 600 rmp for 10 min, and ultrasonicate it at 150 Hz for 10 min (the ultrasonic temperature is 24 °C) to obtain a uniformly mixed electrolyte;

[0069] Step 3: Install the polished and cleaned SS304 on the electrode clamp as the working electrode, and use a platinum sheet as the counter electrode; use a constant voltage DC power supply to electro-deposit the sample, with a deposition voltage of 2 V and a deposition time of 15 min;

[0070] Step 4: Place the deposited wet film in a vacuum oven and dry it at a constant temperature of 40 °C for 3 h. After the film layer on the sample surface is dried, change to 80 °C and dry for 10 h;

[0071] Step 5: Characterize the metal-based bipolar plate containing graphene. The contact resistance of the bipolar plate is as Figure 2 shown to be 15.61 mΩ•cm 2 (under the test condition of 1.4 MPa). The electrochemical test results are as Figure 3 shown that the corrosion current is 26.31 μA / cm 2 (The potentiodynamic polarization test was carried out in a H2SO4 solution with a pH of 3 at 80 °C).

[0072] The test results show that the large sheet structure of graphene effectively enhances the corrosion resistance of the composite coating (comparing Example 1 and Comparative Example 1, the corrosion current density of the modified graphene conductive polymer composite coating has decreased by nearly two orders of magnitude compared with the sulfuric acid sample). In addition, benzenesulfonic acid groups are grafted on the surface of modified graphene, which can dope the conductive polymer, thereby reducing the contact resistance of the composite coating (asFigure 2 as shown

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing a graphene oxide conductive polymer conductive and corrosion-resistant composite coating, which includes the following steps:

[0075] Step 1: The metal-based bipolar plate material is SS304. Use sandpaper (200 mesh and 1000 mesh) to polish the stainless steel surface to remove the surface passivation film; use acetone to remove surface oil stains and fingerprints, use ethanol to remove excess solvent, and put the polished sample into 1 mol / L H2SO4 to further remove the surface passivation film and increase the binding sites on the surface;

[0076] Step 2: Prepare a 1 mg / ml graphene oxide aqueous solution, add pyrrole (0.05 mol / L) to obtain a mixed electrolyte solution, stir the mixed solution at a speed of 600 rmp for 10 min, and ultrasonicate it at 150 Hz for 10 min (the ultrasonic temperature is 24 °C) to obtain a uniformly mixed electrolyte solution;

[0077] Step 3: Install the polished and cleaned SS304 on the electrode clamp as the working electrode, and use a platinum sheet as the counter electrode; use a constant voltage DC power supply to electro-deposit the sample, the deposition voltage is 5 V, and the deposition time is 20 min;

[0078] Step 4: Place the deposited wet film in a vacuum oven and dry it at a constant temperature of 40 °C for 3 h. After the film layer on the sample surface is dried, change to dry it at 80 °C for 10 h;

[0079] Step 5: Characterize the metal-based bipolar plate containing graphene. The contact resistance of the bipolar plate is 40 mΩ•cm 2 (under the test condition of 1.4 MPa), and the electrochemical test results show that the corrosion current is 17.67 μA / cm 2 (the dynamic potential polarization test condition is a H2SO4 solution with PH = 3 at 80 °C). The test results show that the oxygen-containing groups on the surface of graphene oxide cannot effectively dope the conductive polymer, so the contact resistance of the composite coating is relatively high.

[0080] The above embodiments only illustrate the principles and effects of the present invention by way of example, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, characterized in that, It includes the following steps: Step 1: Chemically modify graphene oxide and graft anionic functional groups to prepare a modified graphene oxide aqueous dispersion. The anionic functional groups are benzenesulfonic acid groups, sulfuric acid groups or phosphoric acid groups; When the anionic functional group of the modified graphene oxide is a benzenesulfonic acid group, the preparation method of the sulfonated graphene aqueous dispersion specifically includes the following steps: Step a: Mix the graphene oxide aqueous dispersion with a sodium borohydride solution and stir under a water bath to obtain a pre-reduced graphene oxide dispersion; Step b: Mix aminobenzenesulfonic acid and sodium nitrite in an acidic environment and under an ice bath condition to obtain a diazonium salt solution; Step c: Add the freshly prepared diazonium salt solution to the pre-reduced graphene oxide dispersion and stir under an ice bath condition; Step d: Centrifuge and wash the mixture obtained in Step c multiple times to remove excess reactants and obtain a sulfonated graphene aqueous dispersion; When the anionic functional group of the modified graphene oxide is a phosphoric acid group, the phosphorylated graphene aqueous dispersion includes the following steps: Step a: Slowly drip sodium hydroxide into hydroxyethane diphosphonic acid until the pH value equals 9 - 10; Step b: Mix the graphene oxide aqueous dispersion with the solution obtained in Step a and stir under a water bath for several hours; Step c: Centrifuge and wash the mixture obtained in Step b multiple times to remove excess reactants and obtain a phosphorylated graphene aqueous dispersion; Step 2: Only mix the modified graphene aqueous dispersion and the conductive polymer monomer aqueous dispersion, and mix the modified graphene aqueous dispersion and the conductive polymer monomer aqueous dispersion in a certain proportion to obtain an electrolyte; Step 3: Pretreat the metal-based bipolar plate. Immerse the metal-based bipolar plate in a sulfuric acid solution to remove the passivation film on its surface; Step 4: Use the metal-based bipolar plate as the anode and a platinum sheet as the cathode, and electro-deposit the metal-based bipolar plate with a constant voltage DC power supply; Step 5: Dry the deposited wet film to obtain a graphene conductive polymer composite coating.

2. The method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition according to claim 1, characterized in that, In the above Step 2, the conductive polymer monomers include polypyrrole, polyaniline, and polythiophene.

3. The method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition according to claim 1, characterized in that, In the above Step 2, the electrolyte also includes an initiator, a dispersion aid, and a surfactant.

4. The method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electro-deposition according to claim 1, characterized in that, In the above Step 2, the concentration of the modified graphene aqueous dispersion is 1mg / ml - 4mg / ml, and the concentration of the conductive polymer monomer is 0.01mol / L - 0.15mol / L.

5. A method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition, characterized in that, In the above Step 3, the metal-based bipolar plate is a stainless steel bipolar plate or a titanium alloy bipolar plate. Use sandpaper to polish the surface of the metal-based bipolar plate to remove the surface passivation film, use acetone to remove the oil stains and fingerprints on the surface of the metal-based bipolar plate, and use ethanol to remove the excess solvent.

6. The method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition according to claim 1, characterized in that, In the above Step 4, the deposition voltage is 1 - 5V, and the deposition time is 10 - 20min.

7. The method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition according to claim 1, characterized in that, In the above Step 5, the drying method of the wet film is heating drying, and the temperature range is 40 - 80°C.

8. A method for preparing a graphene conductive polymer coating on the surface of a bipolar plate by electrodeposition method, characterized in that, Place the deposited wet film in a vacuum oven and dry it at a constant temperature of 40°C for 3h. After the film layer on the sample surface is dried, change to 80°C and dry it for 10h.

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