Preparation method of zinc phthalocyanine doped PANI coating on surface of metal bipolar plate

Abstract

The invention discloses a preparation method of a zinc phthalocyanine doped PANI coating on the surface of a metal bipolar plate. The preparation method comprises the following steps of pretreatment of the surface of the bipolar plate, preparation of an electroplating solution, an electro-deposition process and a post-treatment process. According to the preparation method of the zinc phthalocyanine doped PANI coating on the surface of the metal bipolar plate, the functional composite coating which is compact in structure, excellent in conductivity and outstanding in corrosion resistance is prepared by accurately controlling the doping concentration of zinc phthalocyanine and electro-deposition process parameters in the electroplating solution, and the energy efficiency and the service life of a water electrolysis hydrogen production device and a fuel cell system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment of energy conversion devices, and in particular to a method for preparing a zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate. Background Art

[0002] As a key functional component in water electrolysis hydrogen production devices and fuel cell systems, bipolar plates have multiple technical functions: on the one hand, they need to conduct current efficiently to ensure the energy conversion efficiency of the system; on the other hand, they need to distribute reaction gases or liquids and maintain structural stability in harsh electrochemical environments. Especially in the working environment of water electrolysis and fuel cells, bipolar plates are exposed to strong acidic or alkaline electrolytes for a long time, and are affected by electric fields and temperature fluctuations, facing severe corrosion challenges.

[0003] Stainless steel has become the mainstream material choice for bipolar plate manufacturing due to its advantages such as high mechanical strength, good processing performance and moderate cost. However, in practical applications, stainless steel bipolar plates still face two core technical difficulties: one is the high surface contact resistance, which affects the overall energy efficiency of the system; the other is that they are susceptible to corrosion in the electrochemical working environment, which not only shortens the life of the equipment, but also may cause metal ions to dissolve and contaminate the electrolyte or catalyst. These two problems have become important bottlenecks restricting the large-scale commercial application of water electrolysis and fuel cell technology.

[0004] In the prior art, surface coating has been proven to be an effective way to improve the performance of bipolar plates. Conductive polymer coatings, in particular, have attracted widespread attention due to their conductivity and anti-corrosion properties. Polyaniline (PANI), as a typical conductive polymer, has the advantages of simple synthesis process, good environmental stability, and adjustable conductivity, and has been explored for surface modification of bipolar plates. Studies have shown that PANI coating can form a protective passivation film on the surface of stainless steel, while providing an electron conduction channel to effectively reduce contact resistance.

[0005] However, single PANI coating has obvious limitations in practical applications: although PANI has a certain conductivity, its conductivity is difficult to meet the strict requirements of water electrolysis and fuel cells under high current density working conditions, limiting the energy conversion efficiency; traditional PANI coatings have micropores and structural defects, which provide penetration channels for corrosive media.

[0006] In order to overcome the above technical bottlenecks, it is of great practical significance to develop a composite functional coating with both high conductivity and excellent corrosion resistance. Zinc phthalocyanine, as a metal organic complex with a large π conjugated system, has excellent electron transport properties, chemical stability and special molecular recognition ability. Introducing zinc phthalocyanine molecules into the PANI network structure is expected to significantly improve the overall performance of the coating through synergistic effects: on the one hand, it enhances the electron conduction ability and reduces the contact resistance; on the other hand, it optimizes the molecular arrangement structure of the coating and improves its density and corrosion resistance. Summary of the invention

[0007] In view of some shortcomings of the current water electrolysis technology, the main purpose of the present invention is to provide a method for preparing a zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate. By precisely controlling the doping concentration of zinc phthalocyanine and the electrodeposition process parameters in the electroplating solution, a functional composite coating with a dense structure, excellent conductivity and outstanding corrosion resistance is prepared, thereby improving the energy efficiency and life of the water electrolysis hydrogen production device and the fuel cell system.

[0008] In order to solve the above technical problems, a technical solution adopted by the present invention is: a method for preparing a zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate, comprising the following steps: S1. Bipolar plate surface pretreatment: mechanically polish the surface of the stainless steel bipolar plate with sandpaper until the surface presents a mirror effect, wash with deionized water and dry, then chemically clean the polished stainless steel bipolar plate in turn, electrochemically activate the chemically cleaned stainless steel bipolar plate, rinse with deionized water and prepare for subsequent electrodeposition treatment; S2. Preparation of electroplating solution: prepare a basic electrolyte, dissolve zinc phthalocyanine powder in a small amount of N,N-dimethylformamide, slowly drop the dissolved zinc phthalocyanine solution into the above basic electrolyte, while continuously stirring, and ultrasonically treat for 30-60 minutes to ensure that the zinc phthalocyanine is fully dispersed in the electroplating solution, adjust the pH value of the electroplating solution to 0.8-1.5, and deoxygenate the prepared electroplating solution under nitrogen protection for 30 minutes before electroplating; S3. Electrodeposition process: S3.1 Electrolytic cell setup: The pretreated stainless steel bipolar plate is used as the working electrode, the platinum sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The electrolytic cell is made of acid- and alkali-resistant polytetrafluoroethylene material with a working volume of 200-500mL; S3.2 Selection of electrodeposition method: constant potential electrodeposition or pulse electrodeposition; S3.3 Electroplating process control: During the electroplating process, keep stirring the plating solution to ensure uniform dispersion of zinc phthalocyanine, monitor the current-time or potential-time curve in real time to ensure the stability of the electrodeposition process, and terminate the electrodeposition process when the deposition current or charge reaches the preset value; S3.4 Preparation of multilayer composite coating: First, electrodeposit the first pure PANI base layer, then switch to the electroplating solution containing zinc phthalocyanine to deposit the second composite coating layer, and finally electrodeposit the third pure PANI protective layer. Gently rinse with deionized water between each layer, and deposit the next layer without complete drying; S4. Post-treatment process: After deposition, the sample is gently rinsed with deionized water to remove residual electrolyte on the surface, immersed in a dilute sulfuric acid solution to stabilize the doping state of polyaniline, rinsed again with deionized water to neutrality, and finally dried and heat-treated the coating.

[0009] In an embodiment of the present invention, the chemical cleaning in S1 includes the following steps: immersing the polished stainless steel bipolar plate in a NaOH solution with a mass concentration of 10-30 g / L for cleaning, maintaining the temperature at 60-80°C for 5-10 minutes to remove oil stains on the surface of the stainless steel bipolar plate, immersing it in a H2SO4 solution with a volume concentration of 5-15%, treating it at room temperature for 2-5 minutes to remove oxides on the surface of the stainless steel bipolar plate, and ultrasonically cleaning it with deionized water for 3-5 minutes after the cleaning step.

[0010] In an embodiment of the present invention, the electrochemical activation in S1 includes the following steps: placing the chemically cleaned stainless steel bipolar plate in a solution containing 0.1-0.5 mol / L H2SO4 for electrochemical activation, scanning 3-5 cycles in the potential range of -0.2V to +1.0V using cyclic voltammetry, and a scanning rate of 10-200mV / s. After activation, rinse with deionized water and immediately perform subsequent electrodeposition treatment.

[0011] In an embodiment of the present invention, the preparation of the basic electrolyte in S2 includes the following steps: dissolving 0.1-0.3 mol / L of aniline monomer in 0.3-0.5 mol / L of H2SO4 solution, continuously stirring and adding 0.05-0.15 mol / L of p-toluenesulfonic acid as a dopant, and continuing stirring for 15-30 minutes to ensure that the solution is uniform, thereby obtaining a basic electrolyte.

[0012] In an embodiment of the present invention, S2 further includes a step of filtering the obtained electroplating solution using a 0.22 μm microporous filter membrane to remove undispersed particles.

[0013] In the embodiment of the present invention, in S2, the electroplating solution is stored in a brown bottle and protected from light, and is ultrasonically dispersed again for 10 minutes before use.

[0014] In an embodiment of the present invention, in the preparation of S3.4 multilayer composite coating, the electroplating time of the first PANI base layer is 5-10 minutes, the electroplating time of the second composite coating layer is 15-30 minutes, and the electroplating time of the third pure PANI protective layer is 3-5 minutes.

[0015] In an embodiment of the present invention, after the deposition is completed in the post-treatment process, the sample is gently rinsed with deionized water for 3-5 times, and then immersed in a dilute sulfuric acid solution with a pH value of 4 and allowed to stand for 5-10 minutes.

[0016] In the embodiment of the present invention, the coating is dried in S4: naturally air-dried at room temperature for 1-2 hours or dried at 40° C. for 30-60 minutes.

[0017] In an embodiment of the present invention, in S4, the coating is heat treated at 80-120° C. for 1-2 hours under nitrogen protection to enhance the mechanical stability of the coating.

[0018] The beneficial effects of the present invention are as follows: the preparation method of the zinc phthalocyanine-doped PANI coating on the surface of the metal bipolar plate of the present invention prepares a functional composite coating with dense structure, excellent conductivity and outstanding corrosion resistance by accurately controlling the doping concentration of zinc phthalocyanine and the electrodeposition process parameters in the electroplating solution, thereby improving the energy efficiency and life of the water electrolysis hydrogen production device and the fuel cell system, and solving the problems of high contact resistance and corrosion faced by stainless steel bipolar plates in water electrolysis hydrogen production and fuel cells and other devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which: Figure 1 It is a schematic diagram of the metal bipolar plate during electrodeposition of the present invention; Figure 2 This is a test diagram of the polarization resistance of the electrolyte environment of a simulated fuel cell of the present invention; Figure 3 This is a test diagram of polarization resistance of the electrolyte environment of a simulated alkaline electrolytic cell of the present invention; Figure 4 This is the EIS impedance test diagram of the present invention. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Figure 1-4, an embodiment of the present invention includes: a method for preparing a zinc phthalocyanine-doped PANI coating on a metal bipolar plate surface, comprising the following steps: S1. Surface pretreatment of the bipolar plate: mechanically polish the surface of the stainless steel bipolar plate with 400-2000 mesh sandpaper in sequence until the surface presents a mirror effect, wash with deionized water and dry, then chemically clean the polished stainless steel bipolar plate in sequence, immerse the polished stainless steel bipolar plate in a NaOH solution with a mass concentration of 10-30 g / L for cleaning at a temperature of 60-80°C for 5-10 minutes to remove surface oil stains, immerse in a H2SO4 solution with a volume concentration of 5-15%, and treat at room temperature for 2-5 minutes to remove surface oxides, ultrasonically clean with deionized water for 3-5 minutes after the washing step, place the chemically cleaned stainless steel bipolar plate in a solution containing 0.1-0.5 mol / L H2SO4 for electrochemical activation, and scan 3-5 cycles in the potential range of -0.2V to +1.0V (relative to saturated calomel electrode) by cyclic voltammetry at a scanning rate of 10-200 mV / s, rinse with deionized water after activation and immediately perform subsequent electrodeposition treatment; S2, preparation of electroplating solution: dissolve 0.1-0.3mol / L aniline monomer in 0.3-0.5mol / L H2SO4 solution, add 0.05-0.15mol / L p-toluenesulfonic acid as dopant under continuous stirring, continue stirring for 15-30 minutes to ensure that the solution is uniform, prepare a basic electrolyte, weigh an appropriate amount of zinc phthalocyanine powder according to the set concentration (0.5-5mmol / L), dissolve the zinc phthalocyanine powder in a small amount of N,N-dimethylformamide, slowly drop the dissolved zinc phthalocyanine solution into the above basic electrolyte, continue stirring, ultrasonically treat for 30-60 minutes to ensure that the zinc phthalocyanine is fully dispersed in the electroplating solution, filter with a 0.22μm microporous filter membrane to remove undispersed particles, adjust the pH value of the electroplating solution to 0.8-1.5 with 1mol / L H2SO4 or NaOH, and deoxygenate the prepared electroplating solution under nitrogen protection for 30 minutes before electroplating; S3. Electrodeposition process: S3.1 Electrolytic cell setup: The pretreated stainless steel bipolar plate is used as the working electrode, the platinum sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The electrolytic cell is made of acid- and alkali-resistant polytetrafluoroethylene material with a working volume of 200-500mL; S3.2 Selection of electrodeposition method: constant potential electrodeposition or pulse electrodeposition; 3.2.1 Constant potential electrodeposition: Potential range: +0.7V to +1.2V (vs. SCE), deposition time: 10-30 minutes, temperature control: 20±2℃; 3.2.2 Pulse electrodeposition: Turn-on potential: +0.9V to +1.2V (vs. SCE), turn-off potential: +0.3V to +0.5V (vs. SCE); Pulse frequency: 1-10Hz, duty cycle: 30-70%; total deposition time: 20-45 minutes; temperature control: 20±2℃; S3.3 Electroplating process control: During the electroplating process, keep stirring the plating solution to ensure uniform dispersion of zinc phthalocyanine, monitor the current-time or potential-time curve in real time to ensure the stability of the electrodeposition process, and terminate the electrodeposition process when the deposition current or charge reaches the preset value; S3.4 Preparation of multilayer composite coating: First, electrodeposit the first pure PANI base layer, then switch to the electroplating solution containing zinc phthalocyanine to deposit the second composite coating layer, and finally electrodeposit the third pure PANI protective layer. Gently rinse with deionized water between each layer, and deposit the next layer without complete drying; S4. Post-treatment process: After deposition, rinse the sample gently with deionized water for 3-5 times to remove residual electrolyte on the surface; immerse it in a dilute sulfuric acid solution with a pH of 4 and let it stand for 5-10 minutes to stabilize the doping state of polyaniline, and rinse it with deionized water again until it is neutral. Coating drying: natural air drying at room temperature for 1-2 hours, or drying at 40°C for 30-60 minutes; heat treatment: heat treatment at 80-120°C for 1-2 hours under nitrogen protection to enhance the mechanical stability of the coating.

[0022] Testing of corrosion voltage and corrosion current: Use a three-electrode system, first measure the open circuit potential (OCP) until it is stable, then start potential scanning from OCP (usually within the range of ±250mV), record the potential-current data and draw polarization curves, and determine the corrosion current and corrosion potential by Tafel extrapolation.

[0023]

[0024] Polarization resistance test: (1) a mixed solution of 0.5 mol / L sulfuric acid (H2SO4) and 2 ppm fluoride ion (F-) was prepared and heated to 60°C in a water bath; (2) a 30% mass fraction KOH solution was heated to 80°C. The test was carried out in two different solutions with a potential range of -0.6 V to +1.2 V and a scanning rate of 1 mV / s. After fitting by the Tafel extrapolation method, the polarization resistance (ohm, Ω) of the coatings of different preferred embodiments and comparative examples was calculated. Embodiment 1

[0025] Standard electrodeposition process: The surface of the stainless steel (304) bipolar plate 1 was polished with 600, 800, 1200, 1500, and 2000 grit sandpaper in sequence, and ultrasonically cleaned; it was soaked and cleaned in 20 g / L NaOH solution (70°C, 7 minutes) and 10% H2SO4 solution (room temperature, 3 minutes) in sequence, and electrochemically activated in 0.3 mol / L H2SO4 (-0.2 V to +1.0 V, 4 cycles), and the plating solution was prepared: 0.2 mol / L aniline + 0.4 mol / L H2SO4 + 0.1 mol / L p-toluenesulfonic acid + 2 mmol / L zinc phthalocyanine; constant potential method was used for electrodeposition at +0.9 V (vs. SCE) for 20 minutes, and post-processing was performed according to step S4 to obtain a polyaniline / zinc phthalocyanine composite coating with a thickness of 2-3 μm. Embodiment 2

[0026] Pulse electrodeposition process: Prepare the sample and the electroplating solution according to the steps in the preferred embodiment 1, and adopt the pulse electrodeposition method: turn-on potential +1.0V, turn-off potential +0.4V, frequency 5Hz, duty cycle 50%, total time 30 minutes; post-treatment is the same as in Example 1, and heat treatment is added at 100°C under nitrogen protection for 1 hour to obtain a dense and uniform polyaniline-zinc phthalocyanine composite coating with a thickness of 3-4μm. Embodiment 3

[0027] The sample was prepared according to the steps in the preferred embodiment 1, firstly, the first pure PANI base layer 2 was formed by electroplating in an electroplating solution without zinc phthalocyanine for 7 minutes, then the electroplating solution was switched to an electroplating solution containing 3 mmol / L zinc phthalocyanine, and the second composite coating 3 was formed by electroplating using a constant potential method (+0.9 V (vs. SCE)) for 25 minutes, then the second composite coating 3 was formed by switching back to the pure PANI electroplating solution and electroplating for 5 minutes to form a third pure PANI protective layer 4, and the complete post-processing process of S4 was followed to obtain a three-layer composite functional coating.

[0028] Comparative Example 1: PANI coating with standard electrodeposition process: the surface of the stainless steel (304) bipolar plate was polished with 600, 800, 1200, 1500, and 2000 grit sandpaper in sequence, and ultrasonically cleaned; it was soaked and cleaned in 20 g / L NaOH solution (70°C, 7 minutes) and 10% H2SO4 solution (room temperature, 3 minutes) in sequence, and electrochemically activated in 0.3 mol / L H2SO4 (-0.2 V to +1.0 V, 4 cycles), and the plating solution was prepared: 0.2 mol / L aniline + 0.4 mol / L H2SO4 + 0.1 mol / L p-toluenesulfonic acid, and electrodeposited at +0.9 V (vs. SCE) for 20 minutes using a constant potential method, and post-treated according to step S4 to obtain a polyaniline coating with a thickness of 2-3 μm.

[0029] The beneficial effect of the preparation method of the zinc phthalocyanine doped PANI coating on the surface of the metal bipolar plate of the present invention is that the doping concentration of zinc phthalocyanine and the electrodeposition process parameters are accurately controlled in the electroplating solution to prepare a functional composite coating with dense structure, excellent conductivity and outstanding corrosion resistance, and the coating exhibits excellent corrosion resistance in a wide pH range of pH=2-12, and the corrosion current density is 2-3 orders of magnitude lower than that of bare stainless steel. After a long-term immersion test (>1000 hours), the coating still maintains good structural integrity and corrosion resistance, is suitable for long-cycle working environments, improves the energy efficiency and life of water electrolysis hydrogen production devices and fuel cell systems, and solves the problems of high contact resistance and corrosion faced by stainless steel bipolar plates in water electrolysis hydrogen production and fuel cell devices.

[0030] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate, characterized in that: The following steps are involved: S1. Bipolar plate surface pretreatment: mechanically polish the surface of the stainless steel bipolar plate with sandpaper until the surface presents a mirror effect, wash with deionized water and dry, then chemically clean the polished stainless steel bipolar plate in turn, electrochemically activate the chemically cleaned stainless steel bipolar plate, rinse with deionized water and prepare for subsequent electrodeposition treatment; S2. Preparation of electroplating solution: prepare a basic electrolyte, dissolve zinc phthalocyanine powder in a small amount of N,N-dimethylformamide, slowly drop the dissolved zinc phthalocyanine solution into the above basic electrolyte, while continuously stirring, and ultrasonically treat for 30-60 minutes to ensure that the zinc phthalocyanine is fully dispersed in the electroplating solution, adjust the pH value of the electroplating solution to 0.8-1.5, and deoxygenate the prepared electroplating solution under nitrogen protection for 30 minutes before electroplating; S3. Electrodeposition process: S3.1 Electrolytic cell setup: The pretreated stainless steel bipolar plate is used as the working electrode, the platinum sheet is used as the auxiliary electrode, and the saturated calomel electrode is used as the reference electrode. The electrolytic cell is made of acid- and alkali-resistant polytetrafluoroethylene material with a working volume of 200-500mL; S3.2 Selection of electrodeposition method: constant potential electrodeposition or pulse electrodeposition; S3.3 Electroplating process control: During the electroplating process, keep stirring the plating solution to ensure uniform dispersion of zinc phthalocyanine, monitor the current-time or potential-time curve in real time to ensure the stability of the electrodeposition process, and terminate the electrodeposition process when the deposition current or charge reaches the preset value; S3.4 Preparation of multilayer composite coating: First, electrodeposit the first pure PANI base layer, then switch to the electroplating solution containing zinc phthalocyanine to deposit the second composite coating layer, and finally electrodeposit the third pure PANI protective layer. Gently rinse with deionized water between each layer, and deposit the next layer without complete drying; S4. Post-treatment process: After deposition, the sample is gently rinsed with deionized water to remove residual electrolyte on the surface, immersed in a dilute sulfuric acid solution to stabilize the doping state of polyaniline, rinsed again with deionized water to neutrality, and finally dried and heat-treated the coating.

2. The method for preparing the zinc phthalocyanine-doped PANI coating on the surface of the metal bipolar plate according to claim 1, characterized in that: The chemical cleaning in S1 includes the following steps: immersing the polished stainless steel bipolar plates in a NaOH solution with a mass concentration of 10-30 g / L for cleaning, maintaining the temperature at 60-80°C for 5-10 minutes to remove oil stains on the surface of the stainless steel bipolar plates, immersing them in a H2SO4 solution with a volume concentration of 5-15%, treating them at room temperature for 2-5 minutes to remove oxides on the surface of the stainless steel bipolar plates, and ultrasonically cleaning them with deionized water for 3-5 minutes after the cleaning step.

3. The method for preparing the zinc phthalocyanine-doped PANI coating on the surface of the metal bipolar plate according to claim 2, characterized in that: The electrochemical activation in S1 includes the following steps: placing the chemically cleaned stainless steel bipolar plate in a solution containing 0.1-0.5 mol / L H2SO4 for electrochemical activation, scanning 3-5 cycles in the potential range of -0.2V to +1.0V using cyclic voltammetry, and a scanning rate of 10-200mV / s. After activation, rinse with deionized water and immediately perform subsequent electrodeposition treatment.

4. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: Prepare the basic electrolyte in S2 The steps include: Dissolve 0.1-0.3 mol / L aniline monomer in 0.3-0.5 mol / L H2SO4 solution, continue stirring and add 0.05-0.15 mol / L p-toluenesulfonic acid as a dopant, continue stirring for 15-30 minutes to ensure the solution is uniform, and obtain a basic electrolyte.

5. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: S2 further includes the step of filtering the obtained electroplating solution using a 0.22 μm microporous filter membrane to remove undispersed particles.

6. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In S2, the plating solution was stored in a brown bottle and protected from light, and was ultrasonically dispersed again for 10 minutes before use.

7. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In the preparation of S3.4 multilayer composite coating, the electro-deposition time of the first pure PANI base layer is 5-10 minutes, the electro-deposition time of the second composite coating layer is 15-30 minutes, and the electro-deposition time of the third pure PANI protective layer is 3-5 minutes.

8. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: After deposition is completed in the post-treatment process, the sample is gently rinsed with deionized water for 3-5 times and then immersed in a dilute sulfuric acid solution with a pH of 4 for 5-10 minutes.

9. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: Dry the coating in S4: air dry at room temperature for 1-2 hours or dry at 40°C for 30-60 minutes.

10. The method for preparing zinc phthalocyanine-doped PANI coating on the surface of a metal bipolar plate according to claim 1, characterized in that: In S4, the coating is heat treated at 80-120° C. for 1-2 hours under nitrogen protection to enhance the mechanical stability of the coating.

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