Experimental analysis of DMFC cathode temporary degradation

Dedicated OCV tests feeding the anode with a mixture of methanol and hydrogen have been performed to investigate cathode temporary degradation. There is a voltage decay of more than 20 mV between the peak voltage in OCV and the stabilized voltage value, during 20 minutes test. This voltage decay is comparable with the one occurring during nominal operation. Different cathode electrodes have been tested in a wide range of operating conditions, varying methanol concentration, airflow rate, oxygen concentration and cell temperature. Experiments at different methanol concentrations confirm that the recoverable voltage decay is not due to methanol crossover flux. Moreover experimental tests at different cathode humidification exhibit different membrane resistance evolution, while the voltage decay remains the same. Instead, a strong effect of cathode potential on voltage decay is evident. This behavior suggests the possible cathode oxides formation and removal mechanism as the main cause of DMFC temporary degradation.