Nano-Composite Filler of Heteropolyacid-Imidazole Modified Mesoporous Silica for High Temperature PEMFC at Low Humidity

Abstract

Nano-composite filler has received attention for the application to high temperature and low humidity polymer electrolyte membrane (PEM) in fuel cell systems. Heteropolyacids (HPAs) are one of the most attractive materials because of their conductive and thermally stable properties, but have practical limitations due to their high solubility. We investigated the stabilization of HPA on imidazole modified mesoporous silica as a nano-composite filler. The role of mesoporous silica as a support for imidazole and the distribution of chemically bonded HPA on the surface were both confirmed through physical and chemical analysis. The developed nano-composite was utilized to a PEM as a proton conducting filler, cast with commercial Aquivion™ solution. Changing the HPA: imidazole ratio and HPA wt%, the composite membrane of Im10/PWA6/Si-MCM-41 (PWA 10 wt%) resulted in higher proton conductivity compared to the non-modified membrane at all operation conditions, especially at high temperature (140◦ C) and low relative humidity (RH 10%), with values of 0.3530 and 0.0241 S/m, respectively. A single cell test at H2 /Air also showed the effect of adding the nano-composite filler at a wide range of temperatures, which outperformed a single cell with a pristine membrane even at an extremely low humidity condition.