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

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(degrees)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 mu 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 mu m formed due to interstitial nitrogen atoms.