Effect of membrane thickness on the performance and efficiency of passive direct methanol fuel cells

The use of various Nafion membranes, including Nafion 117, 115 and 112 with respective thicknesses of 175 μm, 125 μm and 50 μm, in a passive direct methanol fuel cell (DMFC) was investigated experimentally. The results show that when the passive DMFC operated with a lower methanol concentration (2.0 M), a thicker membrane led to better performance at lower current densities, but exhibited lower performance at higher current densities. When the methanol concentration was increased to 4.0 M, however, the three membranes exhibited similar cell voltages over a wide range of current densities. In contrast, this work also shows the polarization behaviors in an active DMFC when the three membranes were substantially different. Finally, the test of fuel utilization indicates that the passive DMFC with a thicker membrane exhibited higher efficiency.