Role of co₂ in methanol and water transport in direct methanol fuel cells

CO₂ gas produced in a DMFC during methanol oxidation reaction is typically removed out of the cell through the anode channel while liquid fuel mixture is supplied from the anode channel to the anode porous media. This induces a two-phase flow, which makes it difficult to understand mass transport phenomena in a DMFC. This paper discusses the effect of CO₂ on two-phase flow and mass transport phenomena in a DMFC with a multi-dimensional model. The role of CO₂ in controlling water and methanol transport in DMFCs is theoretically investigated. Multi-D DMFC model explains that amount of CO₂ in the anode controls not only water transport by capillary diffusion, but also methanol transport by both molecular diffusion and capillary diffusion. Two DMFCs (conventional cell and CO₂ breathing cell) are fabricated and tested to confirm the theoretical result acquired from the simulation.