Electrochemical Preparation And Corrosion Resistance Of Graphene/Polyaniline/Stainless Steel Composite Bipolar Plates

Proton Exchange Membrane Fuel Cell（PEMFC）is a kind of clean and efficient power supply using hydrogen（H₂）as fuel,which has a wide application prospect in electric vehicles and other fields.Bipolar Plates（BP）are important components of PEMFC and should have good electrical conductivity and corrosion resistance.Stainless Steel（SS）has attracted much attention because of its low price,good air tightness and good electrical conductivity and corrosion resistance.However,in the weakly acidic working medium of PEMFC,corrosive ions such as F^-,Cl^-,SO₄^2-and NO₃^-lead to the decrease of conductivity and corrosion resistance of BP.Polyaniline（PANI）coatings on SS can improve the conductivity and corrosion resistance of BP.However,under the operating conditions of PEMFC,a single PANI coating still cannot meet the requirements of corrosion prevention.The porous structure of PANI with high porosity leads to corrosion at the metal/coating interface.In this paper,reduced Graphene Oxide（rGO）was deposited on PANI coating by cyclic voltammetry,and r GO/PANI/SS composite bipolar plates were prepared.The corrosion resistance of the bipolar plates was further improved by filling PANI holes with r GO.The morphology was observed by transmission electron microscopy（TEM）and scanning electron microscopy（SEM）,the functional group structure was determined by infrared spectroscopy（FTIR）and Raman spectroscopy（Raman）,the molecular conjugation state was determined by UV-vis,and the chemical composition and bonding state was determined by X-ray photoelectron spectroscopy（XPS）.The corrosion resistance of r GO/PANI/SS in simulated cathode environment of PEMFC was studied,and the influence of cathode reactive gas（O₂）,working potential（+0.6V）and long-term immersion（56 days）on the corrosion resistance of r GO/PANI/316L SS bipolar plate was explored.The main research results are as follows:PANI film with a thickness of 53μm is obtained by electropolymerization in ionic liquid 1-ethyl-3-methylimidazole methyl sulfate,and r GO film with a thickness of 10μm is obtained by electrochemical reduction of graphene oxide（GO）in aqueous solution of 0.03M K₂SO₄ at pH=4.PANI presents an intermediate oxidation state,and the interaction between sp² hybrid r GO and PANI enhances the conjugation effect.Continuous dense r GO coating on porous PANI improves the corrosion resistance of the bipolar plate.Oxygen（O₂）has a significant effect on the corrosion resistance of r GO/PANI/316L SS.Under different oxygen content conditions,the passivation current density decreases in order of I_p（N₂）>I_p（DO）>I_p（O₂）.O₂ helps to form a protective passivated film at the membrane/base interface,which improves the corrosion resistance of r GO/PANI/316L SS bipolar plate.The synergistic action of potential（+0.6V）and O₂ enhances the corrosion resistance of r GO/PANI/316L SS.r GO/PANI/316L SS composite coating still has good corrosion resistance after long-term immersion（56 days）.The innovation of this paper:1.The electrochemical synthesis of polyaniline in ionic liquid.2.Graphene/polyaniline composite system was prepared by electrochemical reduction of graphene oxide.3.Explore the corrosion resistance of the bipolar plate after long-term immersion in the simulated cathode working environment.