Reactive O-Species Spillover in Electrocatalytic Oxygen Evolution Reaction: From Fundamentals to Applications.

Recent advancements in catalyst design have shown several new approaches, which are based on dynamic interfacial behavior of catalysts rather than traditional active site modifications. Among these, reactive O-species (*O and *OH) spillover has emerged as a compelling approach that enables the migration of reactive O-species across distinct catalytic domains. This process facilitates active species distribution while eliminating binding limitations to sites and enabling active center components to work together. Therefore, reactive O-species spillover plays a key role in tuning the adsorption properties and reaction mechanism of the oxygen evolution reaction (OER). This review presents a comprehensive discussion of reactive O-species spillover in the OER, starting with basic principles, followed by detailed mechanistic insights, detection techniques, recent advances, and concluding with a future perspective. The effect of spillover on adsorption properties and reaction kinetics to boost catalyst performance has been explained. Strategies such as heterostructure formation, defect engineering, and electronic structure modifications have been discussed to improve spillover kinetics. Both operando characterization techniques and theoretical modeling have been evaluated to detect spillover phenomena. Furthermore, this review identifies the main obstacles to future research while emphasizing the need for accurate interfacial architecture modifications and a comprehensive understanding of fundamental operating mechanisms.