PAF-6 Doped with Phosphoric Acid through Alkaline Nitrogen Atoms Boosting High-Temperature Proton-Exchange Membranes for High Performance of Fuel Cells.

Abstract

High-temperature proton-exchange-membrane fuel cells (HT-PEMFCs) can offer improved energy efficiency and tolerance to fuel/air impurities. The high expense of the high-temperature proton-exchange membranes (HT-PEMs) and their low durability at high temperature still impede their further practical applications. In this work, a phosphoric acid (PA)-doped porous aromatic framework(PAF-6-PA) is incorporated into poly[2,2'-(p-oxydiphenylene)-5,5'-benzimidazole] (OPBI) to fabricate novel PAF-6-PA/OPBI composite HT-PEMs through solution-casting. The alkaline nitrogen structure in PAF-6 can be protonated with PA to provide proton hopping sites, and its porous structure can enhance the PA retention in the membranes, thus creating fast pathways for proton transfer. The hydrogen bond interaction between the rigid PAF-6 and OPBI can also enhance the mechanical properties and chemical stability of the composite membranes. Consequently, PAF-6-PA/OPBI exhibitsan optimal proton conductivity of 0.089 S cm-1 at 200°C, and peak power density of 437.7mW cm-2 (Pt: 0.3 mg cm-2 ), which is significantly higher than that of the OPBI. The PAF-6-PA/OPBI providesa novel strategy for the practical application of PBI-based HT-PEMs.