Direct measurement of methanol crossover fluxes under land and channel in direct methanol fuel cells

Abstract

Methanol crossover in Direct Methanol Fuel Cells (DMFCs) has a drastic adverse effect on the performance of the cell. Thus, the measurement of methanol crossover flux is of a great importance. In this work, a method is developed to separately measure methanol crossover fluxes under the different regions of the flow field geometry, i.e. under the land and under the channel. Such measurements may further our understanding of this complex phenomenon and thus lead to innovative solutions to mitigate the detrimental effects of methanol crossover. In this method, the anode side of the cell is partially catalyzed in the area of interest (land or channel) and blocked by Teflon® films in other areas, whereas the cathode side is always fully catalyzed. The Linear Sweep Voltammetry measurements show that the methanol crossover flux under the land is higher than that under the channel. The higher crossover flux under the land is attributed to under-land convection. It is believed that under-land convection has duel effects: it causes both a higher methanol concentration and a higher methanol crossover flux under the land.