Electrochemical Properties of La0.6A0.4Co0.2Fe0.8O3 (A = Sr, Ca, Ba) as a Bifunctional Electrode for Reversible Solid Oxide Cells

Perovskite oxides are considered as highly active electrodes for reversible solid oxide cells (RSOCs), which show high conversion efficiency in power-fuel and fuel-power modes. In this work, La0.6A0.4Co0.2Fe0.8O3 (A = Sr, Ca, Ba) oxides are synthesized as bifunctional electrodes for RSOCs. Among them, La0.6Ca0.4Co0.2Fe0.8O3 (LCCF) exhibits the best redox performance, which makes it have the highest catalytic activity not only for the oxygen reduction reaction (ORR) but also for the hydrogen oxidation reaction (HOR). This is mainly because LCCF has the highest oxygen vacancy concentration, which promotes the HOR and ORR. In addition, for HOR and ORR processes on LCCF-based equivalent symmetrical cells, the rate-determining steps (RDSs) are the charge transfer reaction and the reduction of O to O–, respectively. When LCCF is used as the electrode material, an RSOC displays the highest discharge/electrolytic water performance in reversible operation conditions. When the fuel gas is H2/H2O, the maximum power density of the LCCF-based cell can reach 271.1 mW cm–2 at 700 °C and the current density of LCCF-based cell reaches −400.2 mA cm–2 at 700 °C and 1.3 V.