Enhanced performance of micro direct methanol fuel cells using long-range capillary mass transfer medium

Abstract

Micro Direct Methanol Fuel Cell (μDMFC) can use high-concentration methanol fuel to achieve high energy density by increasing the mass transfer resistance of methanol. However, the gas–liquid flow will be obstructed with a high mass transfer resistance. It is challenging to find a medium that has high mass transfer resistance and facilitates gas–liquid flow. In this study, a Long-Range Capillary Mass Transfer (LRCMT) medium was constructed by using the capillary in the pore structure of the fiber metal. The LRCMT medium will enhance the mass transfer resistance in a direction favorable for gas–liquid flow and also adjust the methanol concentration to optimal performance at high-concentration operating conditions. Methanol transport in anode structures with the LRCMT medium is analyzed with Finite Element Methods. The medium is produced by chemically etched stainless steel fibers to improve wettability. The effect of the medium on the performance is investigated by electrochemical measurements of the LRCMT-μDMFC. The results show that in an optimal methanol concentration of 7 mol/L for LRCMT-μDMFC at 298 K, the maximum power density is improved by 56%, while the discharge time is extended by 148%. Measurement results also revealed that the methanol crossover has been reduced with the LRCMT medium.