Analysis of Direct Methanol Fuel Cell (DMFC)-Performance via FTIR Spectroscopy of Cathode Exhaust

Water and methanol flux through Nafion (R) and polyaryl-blend membranes prepared at ICVT were studied under DMFC operation. The water, methanol, and CO2 content in the cathode exhaust were measured by FTIR spectroscopy. Both the water and methanol flux turned out to he strongly dependent on tilt, operating temperature and thus on membrane swelling. Apart from this, water flux through the membrane is primarily affected by the gas volume flux on the cathode side. A coupling between water flux and methanol flux was observed, which leads to the conclusion that methanol is transported both by diffusion and by convection caused by the superimposed water flux. Polyaryl-blend membranes showed a reduced diffusive methanol transport when compared to Nafion (R) due to their ditterent internal microstructure. The impact of methanol cross-over on cathode losses at high current density needs further clarification with respect to the prevailing mechanism of methanol oxidation at the cathode.