Hydrogen oxidation mechanisms on perovskite solid oxide fuel cell anodes

Solid oxide fuel cells with (La,Sr)(Ga,Mg)O3 electrolytes and Sr(Ti_0.3Fe_0.7)O₃ anodes and cathodes yield a power density of 0.6 W/cm² at 0.7 V at 800°C in air and humidified hydrogen. The polarization resistance values are 0.085 Ω· cm² for the cathodes and 0.13 Ω· cm² for the anodes. The cell current-voltage characteristics and the anode resistance dependence on hydrogen partial pressure (pH₂) both indicate that adsorption limits the hydrogen oxidation process.Amodel is developedwhere dissociative hydrogen adsorption becomes an increasingly important rate-limiting step, relative to charge transfer, as temperature and pH₂ 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)O₃ anodes and previously-reported data on other oxide anodes.