Quaternized polybenzimidazole efficiently regulates the distribution of phosphate in high-temperature proton exchange membrane fuel cells

Abstract

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) exhibit strong tolerance to impurities in hydrogen, which enhances their potential for practical applications. However, the efficiency of gas, proton, and electron electrocatalytic interfaces remains suboptimal, leading to sluggish cathode reaction kinetics and significantly reducing platinum (Pt) utilization. In this study, quaternary ammonium-functionalized polybenzimidazole (QAPBI), where the quaternary ammonium groups form strong ion pair interactions with phosphate, is employed as a bifunctional ionomer in the cathode catalyst layer (CL). This modification facilitates the regulation of phosphate (PA) distribution within the cathode CL and simultaneously improves proton conduction efficiency. Consequently, well-structured three-phase interfaces are effectively established, and the adsorption of PA onto the catalyst surface is minimized, further enhancing Pt utilization. More importantly, the rapid adsorption of PA onto QAPBI reduces the migration and loss of PA during fuel cell operation, thereby enhancing long-term durability. As a result, the peak power density (PPD) of the QAPBI-based HT-PEMFC is increased by 42 % compared to conventional PTFE-based designs, with a corresponding improvement in durability of 37.5 %.