Triggering a Lattice Oxygen Oxidation Mechanism via Gradient Orbital Coupling for Enhanced OER Performance

The effective activation of lattice oxygen can be triggered by modulating the metal–O covalency to activate the lattice oxygen oxidation mechanism (LOM) for the OER. In this work, we perform a systematic and comprehensive DFT screening across the entire lanthanide series to modulate the Ni–O covalency by constructing Ln–O–Ni orbital gradient coupling. We found that the Ni–O covalency can be maximized by the Gd(4f)–O(2p)–Ni(3d) gradient orbital coupling structure formed by Gd doping. Moreover, this structure effectively activates lattice oxygen for reaction participation by elevating the Ni 3d/O 2p band centers and promoting the formation of oxygen vacancies. Therefore, the OER mechanism changes from the adsorbate evolution mechanism to LOM, accelerating the generation of *OO intermediates, which, in turn, significantly lowers the reaction energy barrier. The as-prepared 2% Gd–NiO sample exhibited remarkable stability (180 h) and a low OER overpotential (235 mV@10 mA cm–2), outperforming most of the reported Ni-based alkaline OER electrocatalysts. Moreover, the Zn–air battery constructed with 2% Gd–NiO achieved an excellent energy conversion efficiency and cycling stability. This work provides a theoretical framework for the design of advanced LOM catalysts.