Completely passive operation of vapor-fed direct methanol fuel cells for portable applications

A vapor-fed DMFC with completely passive operation on both anode and cathode sides was demonstrated and employed for the research of structural parameters and operation under ambient conditions. By applying reference electrodes which were screen-printed on the same ionomer membrane with the working electrodes the potential losses on each side were evaluated separately. Thus, the reason for the losses could be discovered in detail. Comparisons between the air-breathing cathode and the forced air flow cathode between vapor methanol and liquid methanol feed were made with different methanol concentrations. It was found that the water profile on the electrodes, either produced from reaction or from the feed solution, could influence the cell performance dramatically. The different efficiencies of the vapor-fed DMFC were calculated. Due to the methanol crossover the total system efficiency was still very low for the vapor-fed DMFC. However, the fact that the cathodic potential loss for the vapor-fed DMFC in a high current density range is less than that for the liquid DMFC makes the former more attractive than the latter.