(564e) Methanol Transport in a Passive Dmfc Employing a Porous Carbon Plate

We have demonstrated that a passive DMFC with a porous carbon plate, PCP, significantly reduced the methanol crossover and increase both of the fuel efficiency and the power density of the DMFC. The CO2 gas layer formed between the MEA and the PCP was essential for significantly limiting the methanol transport to the anode surface where the gaseous methanol diluted in the CO2 gas. In this study, the effect of the pore structure and thickness of the PCP, as well as the CO2 gas barrier layer, thickness, pressure, and the discharging route whether through the PCP or not, on the methanol transport and the performance of a passive DMFC were investigated. The main factors for controlling the methanol transport were the barrier of the gas layer with CO2, and the properties of the PCP. At the low current densities of less than 60mA/cm2, when no CO2 bubbles are emitted, both the pore structure and thickness of the PCP did not affect the methanol transport and the current voltage relationship. At the higher current densities, CO2 bubbles were evolved through the PCP, and different resistances to the methanol transport were observed depending on the PCP pore structure and thickness. The discharging of CO2 bubbles across the PCP enhanced methanol transport in case of large pore diameter PCP, 42 micro meter in contrast to the small pore diameter one, 1micro meter. The resistivity of the CO2 gas layer increased by increasing its thickness while it not affected by the variation of its pressure in case of PCP with small pore diameter within the measured pressure range.