Surface Hydrogen Bond-Induced Oxygen Vacancies of TiO₂ for Two-Electron Molecular Oxygen Activation and Efficient NO...

Defect engineering can provide a feasible approach to achieving ambient molecular oxygen activation. However, conventional surface defects (e.g., oxygen vacancies, OVs), featured with the coordinatively unsaturated metal sites, often favor the reduction of O₂ to •O₂^- rather than O₂^2- via two-electron transfer, hindering the efficient pollutant removal with high electron utilization. Herein, we demonstrate that this bottleneck can be well discharged by modulating the electronic structure of OVs via phosphorization. As a proof of concept, TiO₂ nanoparticles are adopted as a model material for NaH₂PO₂ (HP) modification, in which HP induces the formation of OVs via weakening the Ti-O bonds through the hydrogen bond interactions. Additionally, the formed Ti-O-P covalent bond refines the electronic structure of OVs, which enables rapid electron transfer for two-electron molecular oxygen activation. As exemplified by NO oxidation, HP-modified TiO₂ with abundant OVs achieved complete NO removal with high selectivity for benign nitrate, superior to that of pristine TiO₂. This study highlights a promising approach to regulate the O₂ activation via an electronic structure modulation and provides fresh insights into the rational design of a photocatalyst for environmental remediation.