The strain-mediated orbital synergy in Co3O4 for enhanced oxygen evolution reaction activity

Abstract

Weak adsorption of oxygen intermediates and unclear stability mechanisms hinder the practical application of spinel oxides such as Co₃O₄ in catalyzing the oxygen evolution reaction (OER). This study indicates the structure-activity relationship between biaxial strain engineering and the electrocatalytic performance on Co₃O₄(100) through electronic structure modulation. Density functional theory (DFT) calculations reveal that the OER predominantly follows the adsorbate evolution mechanism (AEM) with high stability within a -3% to 3% biaxial strain range due to high oxygen vacancy formation energies. Moderate strains significantly enhance catalytic activity by strengthening species adsorption, with -2% compressive strain reducing the potential-determining step energy to 0.28 eV. Conversely, extreme strains (±3%) weaken species adsorption and disrupt the intermediate adsorption/desorption equilibrium, increasing the energy to higher than 0.60 eV. Mechanistic analysis reveals that Jahn-Teller distortion induces asymmetric Co 3d orbital splitting, which strengthens σ-bonding with oxygen intermediates via dz² bonding orbitals’ upshift. However, excessive tensile strain triggers π-antibonding occupancy of intermediates through dxz/dyz antibonding orbital downshifting, weakening the adsorption. Additionally, extreme compression reduces d-orbital hole occupancy via increased coordination, further degrading activity. This work establishes a theoretical framework for precisely tuning d-orbital occupancy in transition metal oxides through lattice strain engineering.