A novel inorganic proton exchange membrane based on self-assembled HPW-meso-silica for direct methanol fuel cells

Direct methanol fuel cells (DMFCs) based on high-temperature (100-300 degrees C) proton exchange membranes (HT-PEMs) offer significant advantages over the current low-temperature DMFCs based on perfluorosulfonic acid (e. g., Nafion (TM)), such as reduction in CO poisoning via faster reaction kinetics, thus increasing the energy efficiency and reducing precious metal loading. This paper reports a novel inorganic proton exchange membrane based on 12-tungstophosphoric acid mesoporous silica (HPW-meso-silica) nanocomposites. The HPW-meso-silica was synthesized via a one-step self-assembly route assisted by a triblock copolymer, Pluronic P123, as the structure-directing surfactant. The threshold of the HPW content in the nanocomposites for the conductivity of mesoporous silica is 5 wt%. The best results were obtained at 25 wt% HPW-meso-silica, delivering a high proton conductivity of 0.091 S cm(-1) at 100 degrees C under 100% relative humidity (RH) and 0.034 S cm(-1) at 200 degrees C under 3% RH and a low activation energy of 14.0 kJ mol(-1). The maximum power density of a cell with a 25 wt% HPW-meso-silica membrane is 19 mW cm(-2) at 25 degrees C and increased to 235 mW cm(-2) at 150 degrees C in methanol fuel.