Effects of Ce co-doping to A site of Sm0.5-xSr0.5CoO3±δ for high performance air electrode of solid oxide reversible cells

Abstract

Oxide perovskite such as SrCoO3, is considered one of the promising air-electrode catalysts for solid oxide cells. SrCoO3 composes of non-precious elements and possesses active catalytic activities for various reactions including an oxygen reduction and an oxygen evolution reaction. However, the catalytic activity of this materials is limited, typically at the reduced temperature. In this study, an effective method to improve the catalytic activities of SrCoO3 was achieved by co-doping of cerium (Ce) and samarium (Sm) at A site (Sr site) of SrCoO3. Although Ce was considered the B-site dopant in term of ionic size and coordination number, small amount of Ce was successfully substituted the Sr site, simultaneously with Sm. Oxygen reduction and evolution activity were significantly increased by substitution of small amount of cerium (~ 2.5 mol %) in A-site. At 973 K, the maximum power density generated from the LaGaO3-supported cell with Ce-Sm co-doped SrCoO3 as an air electrode was 0.62 W cm-2 in fuel cell mode, and the current density in steam electrolysis mode at 1.5 V was 0.93 A cm-2. Increased air electrode activity could be assigned to the improved surface-active sites and electrical conductivity of SrCoO3 by simultaneous substitution of Ce with Sm at A site.