Temperature and methanol concentration dependences of direct methanol fuel cell performance measured by single cell having reference electrode

In this study, we measured the cell temperature and methanol concentration dependences of direct methanol fuel cell (DMFC) performances and its polarization characteristics using a single cell with a Ag/Ag2SO4 reference electrode, which has been developed for the DMFC research in our laboratory. The membrane electrode assembly composed of carbon-supported Pt-Ru and Pt catalysts and the Nafion membrane was used for the measurements. As a result, the power densities obtained while feeding 1 and 5 mol dm−3 methanol solutions increase in the order of 26, 40, and 60 °C. For the 10 mol dm−3 methanol, the power density at 60 °C is lower than those at 26 and 40 °C. In these cases, the polarization curves to investigate the details of the relationship between the DMFC performance and temperature indicate that for the 1 and 5 mol dm−3 methanol, the current densities measured at the same anode and cathode potentials are enhanced with the increasing temperature. As for the 10 mol dm−3 methanol, the current densities at the anode and cathode decrease at 60 °C. To clarify a reason for the particular results of the 10 mol dm−3 methanol, the DMFC performances and the polarization curves at 40 and 60 °C were compared as a function of the methanol concentration. These results demonstrate that the decrease in the DMFC performance at 60 °C by feeding 10 mol dm−3 methanol is attributed to the simultaneous appearance of the O2 crossleak and methanol crossover causing the decline in the methanol oxidation performance at the anode and O2 reduction performance at the cathode.