Effects of hot pressing conditions on the performances of MEAs for direct methanol fuel cells

The effects of hot pressing conditions (hot pressing temperature, pressure and time) on the performances of membrane electrode assemblies for direct methanol fuel cells were investigated. The performances of membrane electrode assemblies (MEAs) were characterized by the polarization curves and electrochemical impedance spectra (EIS). The surface morphologies of the electrodes were observed by scanning electron microscopy (SEM). The compression ratios of electrodes were determined by testing the thicknesses of the anodes and the cathodes before and after the hot pressing process. The MEA which was hot pressed at 135 °C under 80 kg cm⁻² for 90 s, showed the highest power density of 46.0 mW cm⁻² at 80 °C and ambient pressure. As the hot pressing temperature, pressure and time increased, the compression ratios of the anodes and cathodes increased, and the activating time required for MEA to reach optimum performance increased, too. The cell resistances of the MEAs hot pressed at higher hot pressing temperature (135 °C) and pressure (120 kg cm⁻²), or for longer time (90 s), decreased because of the good contact between the membrane and electrodes. The MEAs that were hot pressed under higher temperature (135 °C) and higher pressure (120 kg cm⁻²) benefited for long-time cell operating.