Electrode Properties of La1−xSrxCuO2.5−δ as New Cathode Materials For Intermediate Temperature SOFCs

Abstract

Oxygen-deficient perovskite-type oxides, La 1-x Sr x CuO 2.5-δ (LSCu), have been synthesized in a narrow composition range, 0.15≤x≤0.3. Because of their high oxygen vacancy concentration and excellent electrical conductivity, these materials were characterized as new cathode materials for intermediate temperature solid oxide fuel cells. The electrical conductivity, oxidation state of copper ions, cathodic overpotential, and reactivity with yttria-stabilized zirconia (YSZ) were examined in this study. An orthorhombic perovskite was formed when 15% strontium was doped into lanthanum copper oxide. However, as the concentration of strontium increased to the range of 20% to 30%, the perovskite structure transformed from orthorhombic to tetragonal. The tetragonal La 1-x Sr x CuO 2.5-δ exhibited excellent electrical conductivity, cathodic overpotential behavior, and no reaction with yttria-stabilized zirconia (8YSZ) at 800°C for 1000 hours. The excellent electrical conductivities of these materials were due to the increased concentration of electron holes from strontium addition. Using the current-interruption method, these materials showed low cathodic overpotential because of the existence of a large amount of oxygen vacancies. These oxygen vacancies provide numerous pathways for migration of oxygen ions from electrode surface to triple-phase boundary (TPB) or electrode/electrolyte interface as well as injection into electrolyte. Therefore, LSCu can be a very attractive cathode material for intermediate temperature solid oxide fuel cells.