Analysis Method of Oxygen Reduction Reaction Rate in PEFC Using Pt-Sputtered Catalyst

For widespread use of polymer electrolyte fuel cell (PEFC), it is necessary to reduce the amount of platinum by optimizing the cathode catalyst layer (CCL) structure. Therefore, oxygen reduction reaction (ORR) rate which does not include the mass transfer resistance in CCL should be formulated. To measure the ORR rate which does not include the mass transfer resistance in the CCL, a thin layer electrode was prepared by directly sputtering platinum to microporous layer (MPL) on gas diffusion layer. Dependencies of ORR rate on temperature and relative humidity (RH), were measured and analyzed. From the measurement results, ORR parameters which do not include the effect of mass transfer resistance through the CCL were appropriately determined. The ORR rate and electrochemical surface area (ECSA) depend on RH and a half of RH dependency of ORR rate is ascribed to change in ECSA.