The impact of mass transport and methanol crossover on the direct methanol fuel cell

The performance of a liquid feed direct methanol fuel cell based on a Nafion® solid polymer electrolyte membrane is reported. The cell utilises a porous Pt–Ru-carbon supported catalyst anode. The effect of cell temperature, air cathode pressure, methanol fuel flow rate and methanol concentration on the power performance of a small-scale (9 cm2 area) cell is described. Data reported is analysed in terms of semi-empirical models for the effect of methanol crossover by diffusion on cathode potential and thus cell voltage. Mass transfer characteristics of the anode reaction are interpreted in terms of the influence of carbon dioxide gas evolution and methanol diffusion in the carbon cloth diffusion layer. Preliminary evaluation of reaction orders and anode polarisation agree with a previous suggested mechanism for methanol oxidation involving a rate limiting step of surface reaction between adsorbed CO and OH species.