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

High temperature proton exchange membrane fuel cells (HT-PEMFCs) can offer improved energy efficiency and tolerance to fuel/air impurities, and simplify the heat/water management systems at 100-250°C. The high expense of the proton exchange membranes (HT-PEMs) and their low durability at high temperature still impede their further practical applications of HT-PEMFCs. Herein, phosphoric acid-doped porous aromatic framework (PAF-6-PA) were incorporated into poly [2,2'-(p-oxydiphenylene)-5,5'-benzimidazole] (OPBI) to fabricate a novel PAF-6-PA/OPBI composite HT-PEMs with a straightforward solution-casting method for HT-PEMFCs. The alkaline nitrogen structure in PAF-6 can be protonated with PA, providing additional proton hopping sites, and thus creating the fast pathways for proton transfer, while the porous structure can enhance the retention capacity of the composite membranes for PA. The rigid PAF-6 framework can also enhance the mechanical properties and chemical stability of the composite membranes with strong interaction between PAF-6 and OPBI resulted by the hydrogen bond. Consequently, 10%PAF-6-PA/OPBI exhibited the optimal proton conductivity of 0.089 S cm -1 at 200°C, and the peak power density of 437.7 mW cm -2 , which was significantly higher than that of the pure OPBI membrane (262.6 mW cm -2 ), with a Pt catalyst loading of only 0.3 mg cm -2 in the cell performance tests. The PAF-6-PA/OPBI composite membranes provided a novel strategy to the practical application of PBI-based HT-PEMs. This article is protected by copyright. All rights reserved.