Long-Durability Poly(dibenzofuran-co-terphenyl N-methylimidazole) Copolymer Membranes for High-Temperature Polymer Electrolyte Membrane Fuel Cells

Abstract

Phosphoric acid (PA)-doped polybenzimidazoles (PBIs) are a state-of-the-art membrane for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Herein, we develop a new series of imidazole-containing copolymers with π-conjugated structures and multiple hydrogen bonding sites via straightforward polymerization of dibenzofuran, p-terphenyl, and 1-methyl-2-imidazolecarboxaldehyde. The high reactivity of the dibenzofuran monomer provides P(BF_x%-TP_y%-Im) copolymers with high viscosity, while the π-conjugated and hydrophilic furan units also serve as additional PA-binding sites that facilitate the acid doping and proton conduction. The resulting P(BF_20%-TP_80%-Im)/202%PA membrane demonstrates exceptional performance in H₂–O₂ and H₂–air fuel cells, achieving peak power densities of 1085 and 539 mW cm^–2 at 180 °C, respectively, under ambient pressure and humidification. Notably, the H₂–air cell equipped with this membrane shows remarkable stability, maintaining the high performance at 400 mA cm^–2 and 180 °C, with a voltage decay rate as low as 4.3 μV h^–1 over 720 h, likely the best durability result under these highly stressed conditions.