Physical and electrochemical properties of alkaline earth doped, rare earth vanadates

摘要

The effect of partial substitution of alkaline earth (AE) ions, Sr ~2 and Ca ~2, for the rare earth (RE) ions, La ~3, Ce ~3, Pr ~3, and Sm ~3, on the physical properties of REVO _4 compounds were investigated. The use of the Pechini method to synthesize the vanadates allowed for high levels of AE substitution to be obtained. Coulometric titration was used to measure redox isotherms for these materials and showed that the addition of the AE ions increased both reducibility and electronic conductivity under typical solid oxide fuel cell (SOFC) anode conditions, through the formation of compounds with mixed vanadium valence. In spite of their high electronic conductivity, REVO _4-yttira stabilized zirconia (YSZ) composite anodes exhibited only modest performance when used in SOFCs operating with H _2 fuel at 973 K due to their low catalytic activity. High performance was obtained, however, after the addition of a small amount of catalytically active Pd to the anode.