Enhanced conductivity behavior of titanium-based bipolar plate oxide films through microalloying: First-principles calculations and experimental investigations

Abstract

Presently, the formation of oxide films on the surface of Ti-based bipolar plates results in decreased electrical conductivity. This limitation frequently curtails the operational lifespan of proton exchange membrane fuel cells (PEMFCs). In this study, we engineered Ti alloy bipolar plate materials using an elemental screening process and validated their performance through experimentation. The elemental screening results identified eight elements, specifically Ni, Cr, Mo, Ta, W, Fe, Co, and Zn, as promising candidates for bipolar plate materials. Among these, Mo exhibited a pronounced affinity for incorporation into the TiO2 oxide film. Conductivity measurements of passivated bipolar plates indicated that the Ti–Mo alloy displayed excellent electrical conductivity (1.699 × 1020 Ω m−1). Notably, the introduction of Mo (with an energy level of 1.64 eV) significantly reduced the band gap of the oxide film. Importantly, even after continuous potential oxidation for 10,000 s, the interfacial contact resistance (ICR) of Ti-0.35Mo (9.80 mΩ cm2) remained below the threshold set by the American DOE standard (ICR <10 mΩ cm2). Consequently, this research successfully devised a bipolar plate material utilizing a Ti–Mo alloy and proposed an innovative strategy for improving the conductivity of oxide films in bipolar plate materials via an elemental screening approach.