Excellent high-temperature proton exchange membrane fuel cell derived from a triptycene-based polybenzimidazole with low N–H density and high phosphate tolerance

Abstract

Phosphoric species' toxicity to Pt catalyst has shown a significant impact on the kinetics of the oxygen reduction reaction (ORR) in high-temperature proton exchange membrane fuel cells (HT-PEMFCs), which hinders the technology's commercial potential. Herein, a novel triptycene-based polybenzimidazole (Trip-PBI) was obtained for the first time, and employed as a PEM or binder material for HT-PEMFC. The Trip-PBI membrane outperformed the m-PBI membrane in terms of oxygen permeability at 150 °C (18.6 vs 3.7 Barrer), and the gas diffusion electrodes (GDE) using Trip-PBI as a binder displayed moderate hydrophilicity (PA contact angle: 28°). This successfully addresses the issues of gas transfer restriction and excessive PA diffusion in the PEM to the catalysis layer. As a result, at 160 °C, the MEA using Trip-PBI as the binder exhibits the maximum PPD of 700 mW/cm2, which is 1.84 times that of m-PBI and 1.36 times that of PTFE. Moreover, the H2/O2 cell using Trip-PBI binder also exhibits good stability for 100 h at 160 °C with 0.3 A/cm2 current density.