Proton Exchange Membrane with Excellent Proton Conductivity and Superior Stability for Application at High Operating Temperatures

Elevating the operating temperature can effectively improve the electrode reaction and reduce the mass transfer resistance of a fuel cell caused by a double-phase fluid. Here, a copolymer containing imidazole groups and phosphonic acid groups is designed and prepared, and then, a novel proton exchange membrane (PEM) that possesses an interpenetrating polymer network structure and consists of the copolymer and perfluorosulfonic acid (PFSA) is obtained. Owing to the formed acid-base cross-linking structure, the membrane has a more compact structure, and its dimensional stability and gas permeability are significantly improved. The phosphonic acid and imidazole groups with excellent water retention ability improve the continuity of the hydrophilic region of the PEM, and the continuous acid-base pairs weaken the water dependence of proton conductivity; therefore, the prepared PEM exhibits excellent proton conductivity under high temperature conditions. Under high operating temperatures, a single cell based on the prepared PEM exhibits low impedance and excellent polarization performance; hence, it can operate stably above 100 degree celsius. This paper provides a method to prepare an acid-base composite membrane that is promising for application at low humidity and across a range of temperature zones.