In this study, a single polymer electrolyte membrane fuel cell (PEMFC) in H 2 / /O 2 form with an effective dimension of 5 cm×5 cm as well as a single direct methanol fuel cell (DMFC) with a dimension of 10 cm×10 cm were fabricated. In an existing test station, the voltage-current density performances of the fabricated PEMFC and DMFC were examined under various operating conditions. As expected, DMFC showed a lower electrical performance which can be attributed to the slower methanol oxidation

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... ate in comparison to the hydrogen oxidation. The results obtained from the cell operation indicated that the temperature has a great effect on the cell performance. At 60 °C, the best power output was obtained for PEMFC. There was a drop in the cell voltage beyond 60 °C, which can be attributed to the reduction of water content inside the membrane. For DMFC, the maximum power output resulted at 64 °C. Increasing oxygen stoichiometry and total cell pressure had a marginal effect on the cell performance. The results also revealed that the cell performance improved by increasing pressure differences between the anode and cathode. A unified semi--empirical thermodynamic based model was developed to describe the cell voltage as a function of current density for both kinds of fuel cells. The model equation parameters were obtained through a nonlinear fit to the experimental data. There was a good agreement between the experimental data and the model predicted cell performance for both types of fuel cells.