Optimisation of Perovskite Titanates and Niobates as Anode Materials for SOFCs

摘要

Recent work on titania-doped yttria-zirconias has demonstrated that remarkably good electrochemical performances can be achieved, despite the poor electronic conductivity of these fluorite materials. The low electrochemical resistances obtained clearly demonstrate the beneficial effect of good oxide ionic availability at the electrode-gas interface. Perovskite titanates and niobates offer much higher electronic conductivities, avoiding problems associated with poor lateral conductivity of the electrode; however, the ionic contribution to conductivity is typically quite poor. Various strategies to enhance the electrochemical activities of perovskite related electrode materials have been considered including structural modification, composite formation and chemical doping to enhance catalytic performance and/or ionic mobility. Recent results demonstrate the halving of the area specific resistance of a niobate tungsten bronze anode material by Mn-substitution. This enhancement of activity relates to a decrease in polarisation resistance at larger overpotentials. This enhanced activity due to Mn substitution appears to be correlated with an increase in defect electronic conduction.