In Situ Polymerized Protic Ionogels for Fuel Cells at Elevated Temperatures

Dimethylethylammonium hydrogen sulfate ([DMEA]­[HSO4]) and 1-methylimidazoilum hydrogen sulfate ([MIM]­[HSO4]) as protic ionic liquids are intrinsically proton conductive due to available protons on both cations and anions. Protic ionogels are prepared via in situ radical copolymerization of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, and divinylbenzene in [DMEA]­[HSO4] and [MIM]­[HSO4] for fuel cell application. Ionogels could be stretched to twice their original length with a fracture stress of 20 kPa. Proton conduction in the protic ionogels is dominated by the vehicle mechanism and the conductivity reaches a maximum of 17.1 mS cm–1 at 120 °C. The ionogel resulted from [MIM]­[HSO4] is thermally more stable than that from [DMEA]­[HSO4] and fabricated into an ionogel electrode assembly for a H2/O2 fuel cell. A single fuel cell exhibits a peak power density of 3.9 mW cm–2 under nonhumidified conditions. In situ polymerization of vinyl monomers in protic ILs offers an efficient strategy to construct soft electrolytes toward proton conduction at elevated temperatures.