Phosphoric Acid‐in‐Clay Electrolyte Boosting Polybenzimidazole Membranes for High‐Performance Fuel Cells
Bei Wang, Zhiwei Ling, Qingting Liu, Xudong Fu, Rong Zhang, Shengfei Hu, Feng Zhao, Xiao Li, Xujin Bao, Nanwen Li, Jun Yang
Abstract
Abstract The development of phosphoric acid (PA)‐doped polybenzimidazole proton exchange membranes has progressed at a notably slow pace over the past few decades, primarily because of challenges such as the leaching of PA, plasticization effects, and the poisoning of critical components by free PA. Herein, a novel solid‐state proton conductor, phosphoric acid‐in‐clay electrolyte (PA@halloysite nanotubes (HNTs)), is proposed, which features a 3D proton conduction network. This solid‐state conductor partially replaces liquid PA, alleviating the problem of PA leaching. It exhibits strong interaction with PA (close to PA–PA binding energy), achieving a remarkable proton conductivity of 85.81 mS cm − 1 at 180°C/0% relative humidity (RH). By incorporating PA@HNTs into grafted poly(2,5‐benzimidazole) (g‐ABPBI) via in situ polymerization, a composite membrane with outstanding performance is successfully developed. At a PA@HNTs content of 5 wt.%, the proton conductivity of composite membranes reached 0.080 and 0.127 S cm − 1 at 90 °C/98% RH and 180 °C/0% RH, respectively. This performance is attributed to the large amount of PA contained in PA@HNTs, which establishes a dense hydrogen‐bonding network, facilitating ultrafast proton transport via the combined “packed‐acid mechanism” and “Grotthuss mechanism.” The PA@HNTs/g‐ABPBI membrane provides a promising strategy for fuel cell operation over a wide‐temperature range.