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 cel l based on a phosphotungstic acid electrolyte (PWA) was investigated. It was observed that a parasitic chemical process involving redox reac tions of the reagent gases with the electrolyte caused a coulombic los s and a detrimental effect on the polarization curves. The total consu mption of reagent gases was determined and compared to the Faradaic co nsumption. Polarization curves carried out under constant gas utilizat ion (0.66) showed that the decrease of electrochemical activity with r espect to the experiments conducted with a stoichiometric-excess of re agent gas feed was quite limited. It was observed that the electrochem ical losses were more significant when the cell was operated at low cu rrent density or under open circuit conditions, whereas, the electroch emical activity of the PWA fuel cell appeared to be little affected by the chemical cross-over at high current densities. (C) 1997 Elsevier Science Ltd.