Analysis of the chemical cross-over in a phosphotungstic acid electrolyte based fuel cell

The mechanism of the chemical cross-over in a low temperature fuel cell based on a phosphotungstic acid electrolyte (PWA) was investigated. It was observed that a parasitic chemical process involving redox reactions of the reagent gases with the electrolyte caused a coulombic loss and a detrimental effect on the polarization curves. The total consumption of reagent gases was determined and compared to the Faradaic consumption. Polarization curves carried out under constant gas utilization (0.66) showed that the decrease of electrochemical activity with respect to the experiments conducted with a stoichiometric-excess of reagent gas feed was quite limited. It was observed that the electrochemical losses were more significant when the cell was operated at low current density or under open circuit conditions, whereas, the electrochemical activity of the PWA fuel cell appeared to be little affected by the chemical cross-over at high current densities.