Hydrogen Oxidation Mechanisms on Perovskite Solid Oxide Fuel Cell Anodes

Solid oxide fuel cells with (La,Sr)(Ga,Mg)O 3 electrolytes and Sr(Ti 0.3 Fe 0.7 )O 3 anodes and cathodes yield a power density of 0.6 W/cm 2 at 0.7 V at 800°C in air and humidified hydrogen. The polarization resistance values are 0.085 Ω·cm 2 for the cathodes and 0.13 Ω·cm 2 for the anodes. The cell current-voltage characteristics and the anode resistance dependence on hydrogen partial pressure ( ) both indicate that adsorption limits the hydrogen oxidation process. A model is developed where dissociative hydrogen adsorption becomes an increasingly important rate-limiting step, relative to charge transfer, as temperature and decrease. The model fits the data well for cell voltages >0.5 V, deviations at lower voltages are tentatively explained by an increase in anode oxygen content. The model also fits the electrochemical characteristics of cells with (La,Sr)(Cr,Fe)O 3 anodes and previously-reported data on other oxide anodes.