Modeling study of an air-breathing micro direct methanol fuel cell with an extended anode catalyst region

A three-dimensional model was developed for an air-breathing micro direct methanol fuel cell (mu DMFC) with an extended anode catalyst region on the cell channels. The model was evaluated against experimental studies for a mu DMFC under several anode distribution conditions, and the results showed a close agreement. The model was employed to study if catalysts coated on the fluid-flow channel walls could enhance the power generation performance. Further, the effects of the anode catalyst loading of channel walls on the overall cell and individual electrode performances were examined. The modeling results indicated that the fuel cell with anodes both on the proton-exchange membrane and on channel walls did not show superior performance to the fuel cell with anode catalysts only on the membrane since the overall power generation was mainly limited by the kinetics of the methanol electrode reaction but not the methanol transfer. The modeling results also demonstrated that increasing the anode catalyst loading on channel walls decreased the cathode potential due to an increase in the ohmic loss for the fuel cell with anode catalysts both on the membrane and on channel walls. Reducing channel dimensions decreased the ionic resistance and increased the methanol concentration at the anode and the methanol crossover flux to the cathode.