聚苯胺/不锈钢双极板在H2SO4中腐蚀性能的变化规律

目的提高质子交换膜燃料电池(PEMFC)双极板的耐蚀性。方法采用循环伏安法,在316L不锈钢(SS)表面电合成导电聚苯胺(PANI)膜,制备PANI/316L SS复合双极板。用红外光谱确定PANI官能团结构,用扫描电镜观察表面形貌,用X射线光电子能谱研究PANI膜成分和键合状态。用0.2 mol/L H2SO4模拟PEMFC腐蚀环境,采用极化曲线研究PANI/316L SS耐腐蚀性能,采用开路电位(OCP)和电化学阻抗谱(EIS),研究PANI/316L SS在长期浸泡过程中的腐蚀行为的变化规律。结果PANI膜具有中间氧化态结构,呈现纤维堆积形貌。XPS结果表明,PANI膜中含有C、N、S和O等元素,聚合过程中“对阴离子”SO42?通过“掺杂”进入PANI分子链。涂覆PANI薄膜的316L SS腐蚀电位提高了0.17 V,长期浸泡过程中,OCP介于0.19~0.32 V之间,说明PANI/316L SS的腐蚀倾向降低。浸泡初期,OCP增大对应于膜/基界面处钝化膜的形成;浸泡中期,OCP下降/上升与钝化膜的溶解/修复有关;浸泡后期,OCP持续下降源于钝化膜的溶解。EIS的Nyquist图由高频端容抗弧和低频端扩散尾构成。结论随着浸泡时间延长,PANI膜被氧化,导致“对阴离子”SO42?从PANI中发生“脱掺杂”,使膜电阻增加,容抗弧半径增大。浸泡82天,PANI/316L SS体系仍具有良好的耐腐蚀性能。

Variation of Corrosion Performance of Polyaniline/Stainless Steel Bipolar Plate in H2SO4

The work aims to improve the corrosion resistance of proton exchange membrane fuel cell(PEMFC)bipolar plates.Conductive polyaniline(PANI)films were electrochemically synthetized on the surface of 316L stainless steel(SS)by cyclic voltammetry to prepare PANI/316L SS composite bipolar plates.The PANI functional group structure was determined by FTIR,the surface morphologies were observed by SEM,and the composition and bonding state of the PANI film were investigated by XPS.The corrosion environment of PEMFC was simulated by 0.2 mol/L H2SO4,the corrosion resistance of PANI/316L SS was studied by polarization curve,and the corrosion behavior of PANI/316L SS during long-term immersion was investigated by open circuit potential(OCP)and electrochemical impedance spectroscopy(EIS).PANI film had an intermediate oxidation structure and exhibited fiber packing morphology.XPS results showed that PANI film contained C,N,S and O elements,and the“counter anion”SO4^2?entered PANI molecular chains by“doping”during the polymerization process.The corrosion potential of 316L SS coated with PANI film was increased by 0.17 V and OCP was between 0.19 V and 0.32 V,indicating that the corrosion tendency of PANI/316L SS was decreased during long-term immersion.The increase of OCP at the initial stage of immersion corresponded to the formation of passivation film at the film/base interface,the decline/rise of OCP at the middle stage of immersion was related to the dissolution/repair of passivation film,and the continuous decline of OCP at the later stage of immersion was due to the dissolution of passivation film.Nyquist plots of EIS were composed of the capacitive reactance arc at high frequency end and diffusion tail at low frequency end.PANI film is oxidized,which leads to the“de-doping”of the“counter anion”SO4^2?from PANI,making the film resistance increase and the arc radius of the capacitive reactance increase with the prolonged immersion time.The PANI/316L SS has good corrosion resistance after being soaked in 0.2 mol/L H2SO4 solution for 82 days.