Electrochemical behaviour and surface conductivity of niobium carbide-modified austenitic stainless steel bipolar plate

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• 作者：Lixia Wang ; Juncai Sun ; Bin Kang ; Song Li ; Shijun Ji ; Zhongsheng Wen ; Xiaochun Wang
• 关键词：Proton exchange membrane fuel cell ; Corrosion resistance ; Bipolar plate ; Interfacial contact resistance ; Austenitic stainless steel ; Niobium carbide
• 刊名：Journal of Power Sources
• 出版年：2014
• 出版时间：15 January, 2014
• 年：2014
• 卷：246
• 期：Complete
• 页码：775-782
• 全文大小：1782 K

文摘

A niobium carbide diffusion layer with a cubic NbC phase surface layer (¡«6?¦Ìm) and a Nb and C diffusion subsurface layer (¡«1?¦Ìm) is fabricated on the surface of AISI 304 stainless steel (304 SS) bipolar plate in a proton exchange membrane fuel cell (PEMFC) using plasma surface diffusion alloying. The electrochemical behaviour of the niobium carbide diffusion-modified 304 SS (Nb-C 304 SS) is investigated in simulated PEMFC environments (0.5?M H₂SO₄ and 2?ppm HF solution at 80?¡ãC). Potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy measurements reveal that the niobium carbide diffusion layer considerably improves the corrosion resistance of 304 SS compared with untreated samples. The corrosion current density of Nb-C 304 SS is maintained at 0.058?¦ÌA?cm^?2 and 0.051?¦ÌA?cm^?2 under simulated anodic and cathodic conditions, respectively. The interfacial contact resistance of Nb-C 304 SS is 8.47?m¦¸?cm² at a compaction force of 140?N?cm^?2, which is significantly lower than that of the untreated sample (100.98?m¦¸?cm²). Moreover, only a minor increase in the ICR of Nb-C 304 SS occurs after 10?h potentiostatic tests in both cathodic and anodic environments.