Topotactic Phase Transformation in Vanadium Dioxide through Oxygen Vacancy Ordering with Synergistic Electron Doping via Hydrogenation

Abstract Controlling the insulator‐metal transition (IMT) in correlated oxide system through oxygen vacancy ordering opens up a new paradigm for unlocking exotic structural transformation and physical functionality. Oxygen vacancies serve as a powerful tuning knob for adjusting the IMT property of VO ₂ , though driving topochemical reduction to V ₂ O ₃ remains rather challenging due to structural incompatibility and competing phase instability. Here, a consecutive oxygen‐vacancy‐driven VO ₂ ‐VO _2‐x ‐V ₂ O ₃ topotactic phase transformation route is demonstrated with pronounced facet‐dependent anisotropy, engendering widely tunable IMT properties across an extended temperature range over 200 K. Remarkably, topochemically reduced V ₂ O ₃ inherits the crystallographic characteristics from parent VO ₂ , enabling the possibility of accessing exotic lattice framework with tunable IMT behaviors. Analogous electron doping arising from hydrogenation and oxygen vacancies contributes cooperatively to drive Mott phase transition in VO ₂ through band‐filling control, while ionic interactions between protons and oxygen vacancies markedly accelerate the oxygen ionic mobility. The work not only establishes a framework for engineering physical functionality through defect‐mediated topotactic transition and band filling but also provides fundamentally new insights for filling‐controlled Mott physics.