Lithiation‐Induced Defect Engineering to Promote Oxygen Evolution Reaction

Exploring efficient electrocatalysts for oxygen evolution reaction (OER) is an urgent need to advance the development of sustainable energy conversion. Though defect engineering is considered an effective strategy to regulate catalyst activity for enhanced OER performance, the controllable synthesis of defective oxides electrocatalysts remains challenging. Here, oxygen defects are introduced into NiCo2O4 nanorods by an electrochemical lithiation strategy. By tuning in situ lithiation potentials, the concentration of oxygen defects and the corresponding catalytic activity can be feasibly regulated. In addition, the relationship between the changes in the defect density and electronic structure and the lithiation cut‐off voltages is revealed. The results show that NiCo2O4 nanorods undertook intercalation and two‐step conversion reaction, in which the lithiation‐induced conversion reaction gives rise to a CoO@NiO‐based structure with higher defect density and lower oxidation states. As a result, the defective CoO@NiO‐based catalyst exhibits exceptional OER activity with an overpotential of 270 mV at 10 mA cm−2, which is about 74 mV below the pristine nanomaterials. This research proposes a novel strategy to explore high‐performance catalysts with structural stability and defect control. Controllable oxygen defects are successfully introduced into NiCo2O4 nanorods through an electrochemical lithiation strategy. By tuning in situ lithiation potentials, the concentration of oxygen defects and the corresponding catalytic activity is regulated. Furthermore, the defective CoO@NiO generated by the lithiation‐induced conversion reaction is demonstrated as a potential oxygen evolution reaction catalyst, showing high activity and long‐term stability.