Abstract: The effect of the anode backing layer consisting of carbon papers with different polytetrafluoroethylene(PTFE) contents on the methanol mass transfer and cell performance of a passive direct methanol fuel cell(DMFC) was investigated by methanol permeability measurement. The membrane electrode assemblies(MEAs) were fabricated with the same anode catalyst layer, membrane and cathode. The experimental results showed that the methanol permeability decreased with the increase of PTFE contents in anode backing layer.  It was found that PTFE-treated backing layer results in a lower limiting current density, which could be attributed primarily to the increased mass transfer resistance. When the PTFE content in the anode backing layer is up to 40%, the maximum power density of passive DMFC feeding with 9 mol/L methanol solution can achieve 32×10-3 W/cm2. Moreover, the use of a PTFE-treated backing layer also can decrease water transfer from the anode to the cathode, thus mitigating water flooding problem in the cathode.

Key words: passive direct methanol fuel cell, anodic backing layer, hydrophobicity, methanol mass transfer, cathode water-flooding