Inorganic Lewis Base-Modified Polybenzimidazole for High-Temperature Proton-Exchange Membrane Fuel Cell Applications

Phosphoric acid (PA) leakage restricts the commercialization process of polybenzimidazole (OPBI)-based high-temperature proton-exchange membrane fuel cells (HT-PEMFC). In this work, sulfonated iron–titanium oxide (sFTO) is employed in the OPBI membrane to improve the PA retention ability due to the Lewis base ability of sFTO. The sFTO/OPBI composite membrane therefore exhibits a 237% lower PA leakage than the pristine OPBI membrane resulting from the hydrogen bonding between PA and the Fe–O–Ti network with a high density of vacancies and unpaired electrons. As a result, the sFTO/OPBI membrane reveals a proton conductivity of 0.18 S/cm at 180 °C, which is 257% higher than that of the pristine OPBI membrane due to the stable and rapid proton-conductive channel created in the membrane matrix. HT-PEMFC equipped with sFTO/OPBI can therefore outperform the pristine OPBI membrane by 72% with a maximum power density of 576.18 mW/cm2 at 180 °C. Above all, this work identifies a membrane design route for HT-PEMFC applications.