Relative performance of a liquid-feed polymer-electrolyte direct methanol fuel cell with oxygen and air cathodes at near-ambient pressures

During the last few years, liquid-feed polymer-electrolyte direct methanol fuel cells (DMFC) have attracted considerable research and development efforts since it offers an alternative and relatively simple power source for vehicular applications with intrinsically clean fuel conversion and minimal changes to current refuelling practices. A liquid-feed DMFC consists of an anode at which methanol is electro-oxidised to CO2 through the reaction: CH3OH+H2O --> CO2 up arrow + 6H(+) + 6e and a cathode at which oxygen (usually air) is reduced to water through the reaction: 3/2 O-2 + 6H(+) + 6e(-) --> 3H(2)O. The electrolyte in the cell is a polymer electrolyte, usually Nafion-117(TM). Liquid-feed polymer electrolyte DMFCs have been successfully operated at power densities between 0. 15 and 0.4 Wcm(-2) at operational temperatures ranging between 60-130 degrees C with cathode pressures of ca. 5 bar both during the operation with oxygen and air [1-3]. However, for a higher overall efficiency of the liquid-feed polymer-electrolyte DMFCs, their operation near-ambient cathode pressures are essential [4]. In this paper, we report the relative performance of a 25cm(2) liquid-feed DMFC at 65 and 90 degrees C with oxygen and air cathodes at near-ambient pressures. This DMFC empolys Pt-Ru/C and Pt/C as anode and cathode materials respectively. The power densities obtained during operation of the cell up to 150m/Acm(2) operational current densities (Figs. 1-4) are close to those reported in the literature [1-4] for cells with pressurised cathodes. The data suggest that it is possible to engineer liquid-feed polymer-electrolyte DMFC for use at near-ambient conditions with higher overall efficiencies in relation to DMFCs with pressurised cathodes.