Overcoming the Dilemma between Low Electrical Resistance and High Corrosion Resistance Using a Ta/(Ta,Ti)N/TiN/Ti Multilayer for Proton Exchange Membrane Fuel Cells
Rong Tu, Rui Min, Mai Yang, Yang Yuan, Long Zheng, Qizhong Li, Baifeng Ji, Song Zhang, Meijun Yang, Ji Shi
Abstract
Bipolar plates in proton exchange membrane fuel cells (PEMFCs) are confronted by the dilemma of low contact resistance and high corrosion resistance; this study aimed to simultaneously satisfy these dimensions in a harsh environment. Using thick multilayer coatings can improve the corrosion resistance, but the contact resistance would be largely compromised. To address this challenge, we propose compatible tantalum/titanium-based coatings on 316L stainless steel (SS316L) as bipolar plates for PEMFCs. With the transition layer, the optimal TaN/(Ta,Ti)N/TiN/Ti coating exhibits an ultralow corrosion current density of 0.369 μA·cm−2 (at +0.6 V vs. SCE) and a contact resistance of 6 mΩ cm2 at 138 N/cm2 after 5 h of potentiostatic polarization, both of which meet the standard of the U.S. Department of Energy. Electrochemical impedance spectroscopy (EIS) and an equivalent electrical circuit model further elucidated that TaN/(Ta,Ti)N/TiN/Ti coating significantly impedes the oxidation reaction and dissolution of metals and provides good protection for the SS316L.