Oxygen Evolution Reaction on La1-xSrxCoO3 Perovskites: A Combined Experimental and Theoretical Study of Their Structural, Electronic, and Electrochemical Properties

摘要

The bulk electronic structure, surface composition, conductivity, and electrochemical activity toward the oxygen evolution reaction for the La1-xSrxCoO3 perovskite series (with x = 0, 0.2, 0.4, 0.6, 0.8, 1) are investigated experimentally and theoretically. It is found that Sr substitutions have the effect of straightening the octahedral cage, aligning atoms along the Co-O-Co axis, and increasing the average oxidation state of the Co cations. As a consequence, both the 'ex situ electronic conductivity as well as the activity toward the oxygen evolution reaction are considerably improved. According to density-functional theory calculations, the alignment of the Co-O-Co bonds and the oxidation of the Co cations enhance the overlap between the occupied O 2p valence bands and the unoccupied Co 3d conduction bands, rationalizing the improvement of the conductivity as a function of the Sr fraction. Additionally, a study of the surface properties as a function of the Sr fraction, carried out by X-ray photoelectron spectroscopy (XPS), provides insight both on surface composition and its effects on the OER activity.