A Comprehensive Study of Azole Containing Systems with High Proton Conductivity under Anhydrous Conditions*

As a device that is capable of transferring the chemical energy of hydrogen to electrical energy, the fuel cell is critical for achieving the net zero emissions goal. Among the components in a fuel cell system, the electrolyte is responsible for proton conduction, and its conductivity plays a central role in the overall performance of a fuel cell system. Currently, most proton conduction membranes work under aqueous conditions as water can promote proton conductions. However, this requirement not only inhibits the high-temperature application of fuel cells but also requires the fuel cell to be equipped with an internal humidifier. As a proton donor and acceptor, azole molecules are proposed to facilitate proton conduction through proton hopping. Thus, in this research, we studied 1,2,3-triazole and imidazole and their blends with phosphonic acid as potential candidates for high-conductivity proton conductors under anhydrous conditions. A high proton conductivity in the range of 100 mS/cm was obtained for one of the samples, which is on par with the conductivity of phosphoric acid-doped polybenzimidazole (PBI-PA) under anhydrous conditions. By combining viscosity and diffusion coefficient with conductivity, we find evidence for the proton hopping mechanism in these systems.