Abstract
The full oxidation of ethanol in a direct alcohol fuel cell remains a significant technical obstacle. A thermodynamic model of the cell has been developed, incorporating a mixed solution of methanol and ethanol, which considers the oxidation of methanol as well as the complete and incomplete oxidations of ethanol. If the activities of the catalysts at electrodes are stable, effects of C-C bond cleavage in alcohol and further oxidation of intermediates on the performance of cell can be quantitatively described. The physical driving force of the electrochemical reactions are displayed by using thermodynamics, then the irreversible losses from the ionization activity, ohm resistance, and finite-rate diffusion of fuels are considered, at last the optimization criterion are determined. The optimum power density and optimum efficiency are both the monotonically decreasing functions of the molar concentration of ethanol in the solution. However, the molar concentration of ethanol in cell is suggested smaller than 0.0107 (molcm−3) to balance the two performance indicators. In such a range, the optimum power density and optimum efficiency are greater than 0.7626 (Js−1cm−2) and 19.6%, respectively, and the required molar composition of alcoholic solution at the inlet of the channel, the molar concentration of methanol and three partial current densities in cell are proposed. The research supplies a novel way to improve the performance of direct alcohol fuel cells.
