Electrochemical properties and interfacial contact resistance of plasma ion nitrided titanium as PEMFC bipolar plate

Abstract Plasma ion nitriding was applied to grade 1 titanium, which was used as a bipolar plate a for proton exchange membrane fuel cell (PEMFC). Electrochemical experiments were performed in a solution of pH3 (Sulfuric acid + 0.1 ppm Hydrofluoric acid, 80 °C) required by the Department of Energy (DoE). Air and hydrogen gas was bubbled to simulate cathode and anode environments, respectively. Several experiments (potentiodynamic polarization and potentiostatic), analyses (XRD, EDS, FE-SEM, and EIS), and interfacial contact resistance measurements were performed to evaluate plasma ion nitrided titanium used as a PEMFC bipolar plate. Plasma ion nitrided titanium showed improved corrosion resistance and interfacial contact resistance compared to the titanium substrate. The nitrided layer was approximately 2.0–2.5 μ m, with dense formation of the layer on the titanium substrate. The results of the EDS analysis indicated that a nitrogen diffusion layer of approximately 2.2 μ m formed due to interstitial nitrogen atoms.