Controlling Co 3d/O 2p Orbital Hybridization in LaCoO3 by Modulating the Co–O–Co Bond Angle for Enhanced Oxygen Evolution Reaction Catalysis

Abstract

The orbital hybridization between metal and oxygen of perovskite catalysts can lower the overpotential and enhance the oxygen evolution reaction (OER) activity. This study combines density functional theory with experiments to clarify how Sr/Fe codoping modulates orbital hybridization and enhances OER catalytic activity of LaCoO₃. The as-prepared La_0.50Sr_0.50Co_0.75Fe_0.25O₃ shows remarkable performance with a low overpotential of 310 mV at 10 mA cm^–2 current density and a 107.03 mV dec^–1 Tafel slope, outperforming most state-of-the-art perovskite-based OER electrocatalysts. The experimental results confirm that Sr/Fe codoping enhances the expansion of Co–O–Co bond angles and strengthens the covalency of the Co–O bond in LaCoO₃, leading to enhanced electrocatalytic activity. Moreover, increasing Sr doping reduces the distance between the Co 3d/O 2p center and the Fermi level, decreasing the energy difference between them and enhancing the degree of orbital hybridization between Co 3d and O 2p. As the degree of Co 3d/O 2p orbital hybridization increases, a higher charge transfer was found between the active center and intermediate product, OOH, reducing the energy barrier of the rate-determining step while lowering the overpotential. This study provides thorough insight into the rational design of OER catalysts based on orbital hybridization.