Electropolymerization And Corrosion Resistance Of Polyaniline Flim In Imidazole Phosphate Salt Ionic Liquid

As a clean energy fueled by H₂,proton exchange membrane fuel cell(PEMFC)has broad application prospects in the fields of electric vehicles and stationary power stations.Bipolar plates are an important part of PEMFC,and improving its performance and reducing costs are the keys to PEMFC applications.Stainless steel(SS)is considered to be one of the ideal materials for the preparation of PEMFC bipolar plates.Depositing conductive polyaniline(PANI)on the surface of stainless steel can improve the corrosion resistance of stainless steel bipolar plates while taking into account the conductivity.At present,there is little research on the corrosion resistance of bipolar plates in the working environment of PEMFC cathode and anode at home and abroad.This thesis focuses on the research of PEMFC cathode and anode gas(O₂,H₂),potential(+0.6 V,-0.1 V)and temperature(80?)on the corrosion resistance of PANI/316L SS bipolar plates.The main findings are as follows:1-ethyl-3-methylimidazole diethyl phosphate([EMIM][DEP])ionic liquid,which is not strict to the environment,is used as the electropolymerized electrolyte,aniline is used as the monomer,and oxalic acid is used as the proton acid.The PANI was electropolymerizes on the surface of 316L SS by cyclic voltammetry.The best preparation process conditions for PANI/316L SS are:aniline 0.5mol/L,oxalic acid 3mol/L,cyclic voltammetry scan rate 30m V/s,and scan potential range-0.8-2V.SEM,FTIR,UV-vis,Raman,XPS were used for structural characterization.SEM shows that the surface of the synthesized PANI film is dense and uniform,and FTIR shows that there are stretching vibration peaks of-COOH and O-P-O bonds.UV-vis found that there is an absorption peak caused by the transition between the benzene ring and the quinone ring.XPS results show that there are four elements of C,N,O and P in the PANI film,and the P element has two bonding states:P-O and P=O.There are doped semiquinone radicals C-N^+·stretching vibration in the Raman spectrum.It shows that the synthesized PANI has an intermediate oxidation state structure,and the[EMIM][DEP]anion(CH₃CH₂)₂PO₄^-and the oxalate anion HOOC-COO^-in the PANI film are co-doped.Under simulated cathode working conditions,O₂caused the OCP of PANI/316L SS system to move forward and the corrosion current density decreased,indicating that O₂enhanced the corrosion resistance of PANI/316L SS.As the potential gradually increases,the OCP value increases,and the self-corrosion potential increases,PANI is oxidized,the"counter anion"in the film is dedoped,and an oxide film is formed at the PANI/316L SS interface,and the corrosion resistance increases and the conductivity decreases.When the temperature of the system increases,the OCP of PANI/316L SS shifts negatively.After being polarized at+0.6V,the corrosion potential of the sample decreases significantly at 80°C,and the corrosion resistance decreases.Under simulated anode working conditions,the anode working gas H₂decreased the OCP value of PANI/316L SS and increased the corrosion current density,indicating that the corrosion resistance of the PANI/316L SS system decreased.As the potential decreases,the OCP value of the PANI/316L SS system shifts negatively,the doping degree of the"counter anion"decreases,the passivation film on the surface of the substrate dissolves,and the corrosion resistance of the system decreases.As the temperature of the solution increases,the current density of PANI/316L SS increases and the corrosion resistance decreases.