Modeling of passive alkaline membrane direct methanol fuel cell

• A comprehensive numerical model for passive AAEM-DMFC is developed.
• Role of MPL and effects of porous media wettability are investigated.
• AMPL can act as an effective methanol diffusion barrier.
• Influence of MPL on water transport depends on current density.
• Preferred water distribution and lower methanol crossover can be achieved.

In this study, a two-dimensional two-phase model is developed for a passive alkaline anion exchange membrane direct methanol fuel cell (AAEM-DMFC) to understand the role of micro-porous layer (MPL) and the effect of porous media wettability on species transport. The results indicate that different regions of polarization curve exhibit different dependence on the methanol feed concentration. Anode MPL can act as the methanol diffusion barrier to retard the methanol mass transport and thus mitigate the methanol crossover. This effect becomes more significant by increasing anode MPL hydrophobicity, which facilitates the use of highly concentrated methanol fuel. However, the insertion of cathode MPL and changes in the wettability of cathode porous layers show insignificant effects on the methanol crossover. Moreover, the influence of MPL on the water transport depends on the current density. Less water crossover can be achieved by reducing the water diffusion or enhancing the back-diffusion through the membrane. Ultimately, a favorable water distribution and lower methanol crossover might be achieved by designing porous layers with desired properties. The simulation results presented in this study may help guide the optimization of water management and the mitigation of methanol crossover in passive AAEM-DMFC.