Bismuth Substituted Strontium Cobalt Perovskites for Catalyzing Oxygen Evolution

Abstract

In this study, we employ the concept of inductive effect through substitution with more electronegative/Lewis acidic A-site ions in the cobalt perovskites to alter the O 2p band center and surface hydroxide affinity to promote oxygen evolution reaction (OER) activity and high stability in the basic electrolyte. Galvanostatically charged (fully oxidized, δ ≈ 0) Bi0.2Sr0.8CoO3-δ was shown to exhibit record OER specific activity exceeding not only LaxSr1–xCoO3-δ but also oxidized SrCoO3-δ, one of the most active oxide OER catalysts reported so far. The enhanced OER kinetics of the oxidized Bi0.2Sr0.8CoO3-δ is attributed to greater hydroxide affinity facilitating the deprotonation of surface bound intermediates due to the presence of strong Lewis acidic A-site Bi3+ ions. In addition, no amorphization or compositional change was observed for the surface of the fully oxidized Bi0.2Sr0.8CoO3-δ after OER, where high structural stability is attributed to the higher Fermi level relative to the O 2p band center of Bi0.2Sr0.8CoO3-δ than that of SrCoO3-δ as evidenced by density functional theory (DFT) calculations. This work provides a novel example in the design of highly active oxide catalysts for OER by leveraging the inductive effect.