An improved oxygen reduction reaction activity and CO2-tolerance of La0.6Sr0.4Co0.2Fe0.8O3-δ achieved by a surface modification with barium cobaltite coatings

Abstract

Solid oxide fuel cells (SOFCs) cathode often suffers from the poisoning effect of the contaminants commonly encountered in air such as CO 2 . Here we report an effective approach to enhancing the activity and CO 2 tolerance of the state-of-the-art La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) cathode enabled by a coating of BaCoO 3-δ (BCO), as verified by the electrochemical testings, Raman analyses, and density functional theory calculations. When surface modified with a thin-film BCO coating, LSCF displays a much enhanced ORR activity and an improved durability against CO 2 . For example, anode supported SOFCs with the LSCF cathode coated with BCO coatings show a remarkable peak power density ( P max ) of 0.41 Wcm −2 and a significantly reduced degradation rate in current density of ∼0.08%h −1 at 0.8 V and 700 °C for a period of 300 hs when humidified H 2 (with 3 vol%H 2 O) was used as fuel and air with 8 vol% CO 2 as oxidant. The demonstrated performance is improved when compared with those of the cells with a blank LSCF electrode (a P max of ∼0.36 Wcm −2 and a degradation rate of ∼0.15%h −1 ) under the same conditions. The adsorption energy calculations suggests that BCO coating makes CO 2 adsorption much weaker than LSCF (−0.54 eV versus −1.07 eV). • A BaCoO 3-δ coating has been deposited on La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 cathode surface. • The coating improves the ORR kinetics and durability of cathode in air with CO 2 . • The CO 2 tolerance is confirmed by the experimental and simulation results.