Mixed ionic and electronic behaviour in SrCo1-xScxO3-δ (x = 0.1 and 0.2) perovskites: novel cathode materials for SOFC

Abstract

The oxygen deficient perovskite SrCoO_3-δ could outperform as cathode material in intermediate-temperature solid-oxide fuel cells (IT-SOFC) if a three-dimensional (3C-type) framework were stabilized under the stringent working conditions of SOFC. Here, we demonstrate that the inclusion of moderate amounts of Sc at the octahedral sites leads to the stabilization of a tetragonal P4/mmm perovskite superstructure, where the desired 3C framework is preserved, rather than the undesirable 2H polytype-corresponding hexagonal phase. As SOFC cathodes, we studied the thermal, electrical, and electrochemical characteristics of SrCo_1−xSc_xO_3-δ (x = 0.1 and 0.2) perovskite oxides. These oxides suit the requirements for mixed ionic and electronic conductors (MIEC) oxides because they have a high concentration of oxygen vacancies, strong electrical conductivity, and great thermal stability. With H₂ as fuel and air as the oxidant, single-cell tests for these compositions, in conjunction with La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ (LSGM) as electrolyte and SrMo_0.8Fe_0.2O_3−δ as the anode, produce power densities exceeding 700 mW/cm² at 850 °C.