Effects of carbon dioxide on the performance of anion-exchange membrane fuel cells

Abstract

The effects of CO2 on the performance of an anion-exchange membrane fuel cell were investigated using a three-electrode single cell equipped with a reference electrode. Though the membrane resistance decreased at high current densities in the presence of CO2 via the self-purging mechanism, the cell voltage was significantly lower than that for pure O 2 especially at low current densities even at a very low CO 2 concentration of 100 ppm. The overpotential at the cathode was hardly changed by the presence of CO2, while that at the anode significantly increased in the presence of CO2. It was concluded that carbonate/bicarbonate ions accumulated at the anode during operation, and reduces the ionic conductivity and the pH in the anode catalyst layer, which results in a high overpotential at the anode.