Abstract
Titanium (Ti) is considered as one of the potential base materials for bipolar plates (BPPs) used in proton exchange membrane fuel cells (PEMFCs) due to its resistance to corrosion and relatively low weight. However, its surface undergoes rapid passivation, forming a stable oxide layer that results in high interfacial contact resistance (ICR) with the adjacent components, ultimately degrading cell performance and efficiency. In this study, nitride-based coatings were deposited on the Ti-based substrates using magnetron sputtering to suppress passivation and improve the conductivity. The role of the interlayer in enhancing the adhesion of the top coatings to the substrate was also investigated. Under accelerated PEMFC operating conditions, nitride-based coatings were able to reduce the corrosion current density and ICR to values lower than the U.S. Department of Energy (DOE) targets determined for 2025. Chronoamperometry test at 0.2 V vs. Hg/Hg2SO4 (cathodic operating potential) was conducted to evaluate the durability of the coated samples. The different performance of the coatings was attributed to their different electronic structures. These findings underscore the critical role of nitride chemistry and electronic structure in governing corrosion and interfacial properties. Overall, the findings established Ta nitride coating as an effective coating for surpassing the performance, durability, and conductivity of Ti-based BPPs for next generation of PEMFCs.