Unraveling Oxygen Electrocatalysis Mechanisms on a Thin-Film Oxygen-Deficient Perovskite La_0.6Sr_0.4CoO_3−δ

In this work, a perovskite-structured and oxygen-deficient oxide, La0.6Sr0.4CoO3−δ (LSCO), has been investigated as a model bifunctional thin-film oxygen electrode for alkaline metal–air cells. The rotating disk electrode (RDE) configuration in combination with common electrochemical techniques such as linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were applied to characterize the behavior of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) taking place on LSCO in 0.1 M KOH solution. The results show that the oxygen electrocatalysis process in LSCO follows a multistep charge-transfer pathway. A physics-based, generalized electrochemical model, encompassing two sequential 2e– steps with HO2– as an intermediate species and one parallel 4e– step, has been established to account for the multistep charge-transfer behavior with very satisfactory results, yielding a series of important electrode kinetic transfer coefficients and exchange current densities for the elementary electrochemical reactions considered. Finally, LSCO is found to be a better oxygen electrode for OER than ORR.