Superacid sulfated SnO2 doped with CeO2: A novel inorganic filler to simultaneously enhance conductivity and stabilities of proton exchange membrane

Towards the breaking of the “trade-off” between proton conductivity and stabilities of sulfonated poly(aryl ether sulfone) (SPAES)-based proton exchange membranes, a strategy of compositing with the superacids of sulfated SnO2 (ST) and SnO2-xCeO2 (CSTx) is designed and carried out. The superacids of ST and CSTx have been synthesized by sulfonation of SnO2 with sulfuric acid and subsequently doped with CeO2. By the solution casting approach, the composite membranes are obtained in a homogenous state and show excellent mechanical strength, thermal, dimensional and chemical stability. ST or CSTx in the composite membranes provides excess active sites and forms additional proton-conducting channels by a network of hydrogen bonds. Although with low IEC levels, all the composite membranes show larger water absorption and proton conductivity than the control SPAES membrane. As a result, the SPAES-2CST3 membrane achieves a power output of 673.6 mW/cm2 at 80 °C, which is higher than the control membrane (481.8 mW/cm2). The durability of the SPAES-2CST3 membrane under accelerated stress test conditions is significantly enhanced compared to the control SPAES membrane, and the aged SPAES-2CST3 membrane exhibits lower hydrogen crossover and better cell performance than the aged control SPAES membrane.