Synergistic Hydrogen-Bonding and Covalent Crosslinking in Polybenzimidazole Membranes for Wide-Temperature Anhydrous Fuel Cells.

Expanding the operational temperature range and reducing the humidity dependence of proton exchange membrane fuel cells (PEMFCs) remain critical challenges. To address these issues, we developed a dual-network architecture that integrates a thermally reinforced hydrogen-bonding matrix with an amine-anhydride covalent crosslinking framework within Tröger's Base (TB)-functionalized polybenzimidazole membranes. The covalently crosslinked TBAm-PBI-TB membrane with dual-network architecture exhibited a high phosphoric acid uptake of 469.5% with negligible leaching and achieved proton conductivities of 255.5 mS cm⁻ ¹ at 90°C and 20% relative humidity (RH) and 264.7 mS cm⁻ ¹ at 160°C under anhydrous conditions. It also demonstrated excellent oxidative and mechanical stability. A membrane electrode assembly (MEA) based on the TBAm-PBI-TB membrane delivered peak power densities ranging from 108.6 to 446.2 mW cm⁻ ² between 30 and 160°C under anhydrous H₂/air conditions. This maximum power density exceeds that of a Nafion 211-based MEA, which reached 367.8 mW cm⁻ ² at 30°C under 40%-50% RH. The MEA also showed outstanding operational durability. This work presents a strategy for developing wide-temperature proton-conducting membranes for anhydrous fuel cells.