Development of high-power electrodes for a liquid-feed direct methanol fuel cell

摘要

Based upon Nafion 112 membrane, membrane-electrode assemblies for a liquid-feed direct methanol fuel cell (DMFC) were fabricated by using a novel method of modified Nafion solution and tape-casting, with unsupported Pt-Ru as an anode catalyst and carbon supported 40 wt.% Pt as a cathode catalyst. The amounts of catalyst loading were controlled to be 4 mg/cm~2 in the anode and 1.3 mg/cm~2 in the cathode. Morphological characteristics of anode and cathode were examined by scanning electron microscopy (SEM). A time-delayed activation effect was found in single cell tests and attributed to time-dependent wetting behavior of Nafion polymers within both catalyst layers. A high compression of the single cell leads to a remarkable decrease in diffusion-limiting current density, caused by hydrophilic broken fibers and cleavage-like defects generated during excessive compression of the cell. A maximum power density of 0.21 W/cm~2 is achieved in 2 M CH_3OH solution at 90℃ under the operating condition of non-pressurized anode side and non-humidified air pressurized to 15 psi.