Ternary Triazole-Based Organic-Inorganic Proton-Conducting Hybrids Based on Computational Models for HT-PEMFC Application

Abstract

We reported a new ternary hybrid anhydrous proton-conducting material based on triazole (Tz), wherein it interacted with TiO₂ and cesium hydrogen sulfate (CHS) constructed based on the acid-base interaction. It exhibited high proton conductivity derived by the two acid-base interactions: between CHS and Tz and between Tz and TiO₂. As a starting point of discussion, we attempted to theoretically predict the high/low proton conductivity using the push-pull protonated atomic distance (PAD) law, which makes it possible to predict the proton conductivity in the acid-base part based on density functional theory. The calculations indicate the possibility of achieving higher proton conductivity in the ternary composites (CHS·Tz-TiO₂) involving two acid-base interactions than in binary hybrids, such as CHS·Tz and TiO₂-Tz composites, suggesting the positive effect of two simultaneous acid-base interactions for achieving high proton conductivity. This result is supported by the experimental result with respect to synthesized materials obtained using the mechanochemical method. Adding TiO₂ to the CHS·Tz system causes a change in the CHS·Tz interaction and promotes proton dissociation, producing a new and fast proton-conducting layer through the formation of Tz-TiO₂ interaction. Applying CHS·Tz-TiO₂ to high-temperature proton exchange membrane fuel cells results in improved membrane conductivity and power-generation properties at 150 °C under anhydrous conditions.