Effect of methanol concentration on passive DMFC performance

A passive, air-breathing, liquid-feed direct methanol fuel cell (DMFC), with no external pumps or other auxiliary devices, was designed, fabricated and tested with different methanol concentrations. It was found that the cell performance was substantially improved with an increase in methanol concentration; a maximum power density of 20 mW/cm2 was achieved with 5.0 M methanol solution. The measurements indicated that the better performance with higher methanol concentrations was mainly attributed to the increase in the cell operating temperature caused by the exothermic reaction between permeated methanol and oxygen on the cathode. This finding was subsequently confirmed by the fact that the cell performance was degraded when the cell running with higher methanol concentrations was cooled to room temperature.