Effect of anode micro-porous layer on species crossover through the membrane of the liquid-feed direct methanol fuel cells

In this work, a two-dimensional two-phase mass transport model is applied to study the mass transport processes of methanol and water through the membrane electrode assembly of the liquid-feed direct methanol fuel cells (DMFCs). Emphasis is placed on exploring the influences of the structural properties of the anode micro-porous layer (MPL) on water and methanol crossover through the membrane. It is indicated that both the rates of water and methanol crossover can be reduced by thickening the anode MPL resulting from the increased mass transport resistance in the MPL. It is also shown that lowering anode MPL permeability by reducing the mean pore size of the MPL or avoiding the formation of mud cracks in the MPL can lower the liquid saturation in the anode, thus reducing both the rates of water and methanol crossover. In addition, it is found that increasing the anode MPL contact angle can significantly reduce the rate of methanol crossover, but it has little impact on water crossover.

► Both the rates of water and methanol crossover can be reduced by thickening the anode MPL.
► Lowering the anode MPL permeability lowers the rates of water and methanol crossover.
► Increasing the anode MPL contact angle highly reduces the methanol crossover rate.
► Variation of the anode MPL contact angle has little impact on water crossover.