Phase‐Guided Assembly of RuO 2 Epitaxial Films on TiO 2 Nanofibers: Interfacial Coherence Outperforming Defect‐Driven Mismatch for Active Site Generation in Li–O 2 Batteries

Abstract Controlling the catalyst‐support interface is essential for achieving high efficiency with reduced noble metal usage. In this work, a phase‐tunable TiO 2 nanofiber scaffold is developed via electrospinning and thermal annealing to regulate the interfacial growth of rationally loaded RuO 2 . The phase of TiO 2 (anatase versus rutile) strongly influences lattice matching, oxygen vacancy formation, and RuO 2 nucleation. Structural and chemical analyses (scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, and electrochemical surface area measurement) confirm distinct RuO 2 morphologies and catalytic site accessibility depending on the TiO 2 crystal phase. Notably, rutile‐based composites form conformal RuO 2 domains with enhanced contact and defect‐assisted conductivity. Electrochemical testing reveals that rutile‐RuO 2 cathodes achieve lower overpotentials (≤0.94 V) and higher cycling stability compared to the anatase counterparts. Furthermore, post‐cycling transmission electron microscopy analysis indicates that the phase‐engineered interfaces facilitate more reversible Li 2 O 2 decomposition. These findings highlight the strong interplay between the oxide phase, interfacial bonding, and catalytic behavior. This work provides a scalable and efficient strategy to extract maximum performance from minimal RuO 2 loading in Li‐O 2 batteries.