Influence of Chemical Operation on the Electrocatalytic Activity of Ba0.5Sr0.5Co0.8Fe0.2O3-delta for the Oxygen Evolution Reaction

Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is a promising electrocatalyst for the oxygen evolution reaction (OER) in alkaline solution. The OER activities of BSCF are gradually enhanced by prolonging the duration of electrochemical operation at OER potentials, but the underlying cause is not fully understood. In this study, we investigated the role of chemical operation, equivalent to immersion in alkaline solution, in the time-course of OER enhancement of BSCF. Interestingly, the time-course OER enhancement of BSCF was promoted not only by electrochemical operation, which corresponds to potential cycling in the OER region, but also by chemical operation. In situ Raman measurements clarified that chemical operation had a lower rate of surface amorphization than electrochemical operation. On the other hand, the leaching behavior of A-site cations was comparable between chemical and electrochemical operations. Since the OER activity of BSCF was stabilized by saturating the electrolyte with Ba2+, "chemical" A-site leaching was key to inducing the time-course OER enhancement on perovskite electrocatalysts. Based on these results, we provide a fundamental understanding of the role of chemical operation in the OER properties of perovskites.