Effect of anode diffusion layer (GDL) on the performance of a passive direct methanol fuel cell (DMFC)

One of the most significant obstacles for passive direct methanol fuel cells is the methanol crossover, since methanol diffuses through the membrane generating heat but no power. This can be reduced if the cell operates with low methanol concentrations. However, this significantly reduces the energy density of the system since a large amount of water is presented on the anode side that will produce no power. Also, water crosses the membrane towards the cathode flooding it and reducing the cell performance. In the present work, different anode diffusion layers were tested in order to select optimal working conditions at high methanol concentrations. The results showed that the performance increased with an increase of carbon cloth thickness due mainly to a decrease of methanol crossover. Regarding the carbon paper, better performances were achieved for lower thicknesses and with a microporous layer (MPL) mainly due to a decrease of the anode overpotential achieved by a facilitated access of reactants. In this work, the best performance was achieved using carbon cloth for a methanol concentration of 3 M with a corresponding power density of 24.2 mW/cm2.