Effect of flow fields on the performance of micro-direct methanol fuel cells

This study evaluated the performance of micro-direct methanol fuel cells (DMFCs) with four kinds of flow fields fabricated on silicon wafers by microelectromechanical system (MEMS) technology. The flow fields and membrane electrolyte assembly (MEA) of 2.25 cm2 active area were assembled to micro-DMFCs. These micro-DMFCs yielded the maximum power densities ranged from 11 to 23 mW cm−2 for the methanol solution concentrations of 1 M, 2 M, 3 M, 4 M and 5 M at the temperature of 20 ± 1 °C. The maximum power densities implied that under the ambient temperature and low flow rate of methanol solution, performance of micro-DMFCs with different flow fields was sorted as: double-channel serpentine (DSFF) > single-channel serpentine (SSFF) > mixed multichannel serpentine with wide channels (MMFW) > mixed multichannel serpentine with narrow channels (MMFN) flow field. Increasing the flow rate of methanol solution from 0.0503 to 0.1128 ml min−1, performance of all micro-DMFCs was improved. Further increasing the rate to 0.3479 from 0.1128 ml min−1, the maximum power densities of micro-DMFCs with MMFW and MMFN increased, however, those of micro-DMFCs with SSFF and DSFF decreased. When the electric load was changed, the micro-DMFC with SSFF took a longer time to reach a stable power output than other micro-DMFCs.