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

Abstract

Oxide perovskites, such as SrCoO₃, are considered to be promising air electrode catalysts for solid oxide cells. SrCoO₃ is composed of non-precious elements and possesses catalytic activity for various reactions, including an oxygen reduction and an oxygen evolution reaction. However, the catalytic activity of this material is typically limited at reduced temperatures. In this study, the catalytic activity of SrCoO₃ was improved by co-doping of cerium (Ce) and samarium (Sm) at the A site (Sr site) of SrCoO₃. Although Ce was considered the B-site dopant in terms of ionic size and coordination number, a small amount of Ce was successfully substituted at the Sr site, simultaneously with Sm. Oxygen reduction and evolution activity were significantly increased by substitution of a small amount of cerium (∼2.5 mol%) at the 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. The increased air electrode activity could be assigned to the improvement in the surface active sites and electrical conductivity of SrCoO₃ by simultaneous substitution of Ce with Sm at the A site.