Effect of oxygen and methanol supply modes on the performance of a DMFC employing a porous plate

Abstract

The effect of oxygen and methanol supply modes on the performance and the fluxes of methanol and water through the membrane electrode assembly, MEA, of a DMFC with and without a porous plate was investigated. For the conventional MEA, MEA C, flowing oxygen and methanol were essential to stabilize the cell performance, avoiding flooding at the cathode and depletion of methanol at the anode. As a result of flowing oxygen, methanol and water fluxes through the MEA C increased by more than twice that for the air-breathing cell. For the MEA with a porous plate, MEA/PCP, the flow of oxygen and methanol had no significant effect on the cell performance, where the porous carbon plate, PCP, prevented the cathode from flooding by reducing the mass transport through the MEA. Methanol and water fluxes through the MEA/PCP were not affected by flowing oxygen at 0.1 l min −1. However, the increase in oxygen flow rate from 0.1 l min −1 to 1 l min −1 had a negative effect on the cell performance either in the MEA C or in the MEA/PCP. This would be due to the cooling effect for MEA C and the drying effect for the MEA/PCP. A moderate supply of oxygen to the cathode, like air-breathing, was appropriate for the DMFC with a PCP.