Spin-State Regulation of Perovskite Cobaltite to Realize Enhanced Oxygen Evolution Activity

Perovskite electrocatalysts strongly rely on electronic structure regulation, especially for electron configuration (e(g)) and conductivity. However, current regulation strategies inevitably involve ambiguous entanglement of crystals, electrons, and spin degrees of freedom. Here, we developed a spin-state regulation method to optimize oxygen evolution reaction (OER) activity by lattice orientation control of LaCoO3 epitaxial films. The different lattice-oriented LaCoO3 films bring different degrees of distortion of the CoO6 octahedron, successfully inducing a spin-state transition of cobalt from a low spin state (LS t(2g)(6) e(g)(0)) to an intermediate spin state (IS t(2g)(5) e(g)(1)). X-ray absorption spectroscopy of Co L-edge and O K-edge provides experimental support of spin-state transition in different lattice-oriented LaCoO3 films. As expected, LaCoO3 (100) film possesses optimal e(g) electron filling, lower adsorption free energy, and higher conductivity, exhibiting better OER performance than the other two films. Our findings demonstrate that electronic state regulation will be a new avenue for the rational design of high-activity perovskite electrocatalysts.