Proton conduction in metal pyrophosphates (MP2O7) at intermediate temperatures

Intermediate-temperature fuel cells have received much recent attention as next generation energy sources. In particular, current efforts are devoted to developing proton conductors that operate at 120 degrees C or more and at low relative humidity. Proton conduction in several metal pyrophosphates (MP2O7, M = Sn, Ti, Si, Ge, Ce, and Zr) that have the potential to meet the demands for intermediate-temperature fuel cell applications are reviewed with an emphasis on the material aspects.