Understanding the Degradation of La1−x Sr x FeO3−δ (0 ≤ x ≤ 1) Perovskite Oxides during the Oxygen Evolution Reaction in Alkaline Solution

Abstract

Perovskite oxides are an emerging class of highly active catalysts for the oxygen evolution reaction (OER); however, their electrochemical stability remains poorly understood. Here, we report a systematic evaluation of the OER activity and stability of La1−x Sr x FeO3-δ perovskites in 1 M KOH. Their initial OER activity first increases with increasing Sr content (from x = 0 to 0.8), and then decreases when the Sr content is increased to 1. Their stability evaluated by monitoring the element leaching from the electrodes show that La does not leach at a detectable rate, but Sr and Fe leach substantially. The leaching of Sr occurs at similar rates under open circuit potential (OCP) and OER potential, suggesting a nonelectrochemical dissolution process. The leaching of Fe is, however, strongly dependent on the electrode potential. More Fe leaching is observed under the OER potential than OCP. Additionally, the electrode with higher initial OER activity leaches more Fe. These results indicate that OER facilitates the dissolution of Fe from the electrode. The leaching of Fe, in turn, is considered responsible for the activity loss of La1-x Sr x FeO3−δ during OER. This study brings new insight into the degradation mechanism of La1-x Sr x FeO3−δ and their related perovskite oxides during electro-oxidation processes.