Surface Hydrogen Bond-Induced Oxygen Vacancies of TiO 2 for Two-Electron Molecular Oxygen Activation and Efficient NO Oxidation.

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 O 2 to •O 2 - rather than O 2 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, TiO 2 nanoparticles are adopted as a model material for NaH 2 PO 2 (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 TiO 2 with abundant OVs achieved complete NO removal with high selectivity for benign nitrate, superior to that of pristine TiO 2 . This study highlights a promising approach to regulate the O 2 activation via an electronic structure modulation and provides fresh insights into the rational design of a photocatalyst for environmental remediation.