A single proton exchange membrane fuel cell (PEMFC) and associated hardware were designed for high-temperature membrane electrode assembly (MEA) testing and diagnosis in the range of . The fuel cell heating strategy and its design considerations with respect to heat balance are also discussed in this paper. The fuel cell performance of PEMEAS -doped polybenzimidazole (PBI)-based MEAs and the corresponding ac impedance diagnosis demonstrated that this single cell and its associated hardware designs are feasible for high-temperature MEA testing. The apparent exchange current densities for the cathodic oxygen reduction reaction as a function of temperature were obtained through ac impedance measurement. Rapid performance degradation was observed at extreme temperatures, such as , suggesting an accelerated fuel cell testing method. AC impedance results showed that the activity loss of the catalyst/catalyst layer was responsible for this degradation.