Local Lattice Softening in Spinel Oxides Induces Lattice Oxygen Activation for Efficient Catalysis

The oxygen evolution reaction (OER) is important for the development of renewable energy systems, where activating lattice oxygen is a key strategy for improving performance. Compared to the conventional adsorbate evolution mechanism (AEM), more resonant vibrational responses in the lattice oxygen mechanism (LOM) promote the bond formation and facilitate catalytic efficiency. Here, we reveal the intrinsic mechanism of the AEM-LOM transition from a vibrational perspective induced by localized lattice softening. Using spinel Co₃O₄ as a model system, theoretical calculations show that Yb introduction lowers the energy barrier of the potential-determining step from 1.794 to 1.048 eV and enables direct lattice oxygen involvement. Phonon density of states (DOS) analysis further reveals that Yb introduction softens the local Co-O framework and modifies the lattice response to oxygen-vacancy (V_O) formation. The redistribution of phonon modes and weakened Co-O vibrational coupling induced by the local octahedral distortion lead to lattice softening. Factor group analysis and irreducible representation decomposition further support that the lattice symmetry breaking in Yb-doped Co₃O₄ is the structural origin of the lattice softening. This work provides a vibrational interpretation of OER mechanism switching in spinel Co₃O₄, offering theoretical insights for the development of more efficient OER electrocatalysts.