Protonic Conductivity of Undoped High-Temperature Polymer Electrolyte Membranes

Xinwei Sun, Truls Norby
University of Oslo

Nafion® is considered a state-of-the-art polymer electrolyte membrane (PEM) for low temperature fuel cells. However, water management, expensive noble metal catalysts, slow electrode kinetics, CO poisoning, and heat recovery remain as key issues limiting performance and system economy. As a result, there is emerging interest in polymer based proton conductors as alternatives to Nafion® with comparable protonic conductivity, but at the same time providing high durability and longer lifetime operating at higher temperatures (> 80 ˚C). Commonly investigated high-temperature PEMs comprise polybenzimidazole (PBI) and polyetheretherketone (PEEK) doped with various strong inorganic acids, operating at a typical temperature range of 80–200˚C. However, less research is available with respect to protonic conduction in the undoped high-temperature polymer membranes. For this reason, the protonic conductivity of undoped PBI and PEEK of various densities is investigated in terms of operating temperature and relative humidity. This contributes to the fundamental understanding of the properties of undoped high-temperature PEM, which in turn may be important for systematic strategies of doping and fillers and other developments to optimise properties and performance.