Asymmetric design of anode and cathode current collectors for micro direct methanol fuel cells

This paper studied the combined effect of anode and cathode current collectors on the behavior of water and methanol crossover in micro direct methanol fuel cells (ÎDMFC). A two-phase, two-dimensional, isothermal model was built to analyze the mass transport behavior in the membrane electrolyte assembly (MEA). The results show that the distribution of methanol exhibits uniform concentration feature over the anode porous area with the asymmetric anode and cathode current collectors. Also, lower water content gradient across the membrane is found. Comparing experiments were conducted to verify the simulation results. Two passive ÎDMFCs were fabricated and tested. The cells presents almost the same performance at relatively low methanol concentration. However, an increase of 10% cell performance (from 27.5 mW.cm-2 for symmetric current collectors to 30.3 mW.cm-2 for asymmetric current collectors) at 5 mol.L-1 methanol solution was observed. This reveals that the couple of asymmetric current collectors induced the methanol to distribute uniformly and largely suppressed the water and methanol crossover.