N-Rich Doped Anatase TiO₂ with Smart Defect Engineering as Efficient Photocatalysts for Acetaldehyde Degradation

Nitrogen (N) doping is an effective strategy for improving the solar-driven photocatalytic performance of anatase TiO₂, but controllable methods for nitrogen-rich doping and associated defect engineering are highly desired. In this work, N-rich doped anatase TiO₂ nanoparticles (4.2 at%) were successfully prepared via high-temperature nitridation based on thermally stable H₃PO₄-modified TiO₂. Subsequently, the associated deep-energy-level defects such as oxygen vacancies and Ti³⁺ were successfully healed by smart photo-Fenton oxidation treatment. Under visible-light irradiation, the healed N-doped TiO₂ exhibited a ~2-times higher activity of gas-phase acetaldehyde degradation than the non-treated one and even better than standard P25 TiO₂ under UV-visible-light irradiation. The exceptional performance is attributed to the extended spectral response range from N-rich doping, the enhanced charge separation from hole capturing by N-doped species, and the healed defect levels with the proper thermodynamic ability for facilitating O₂ reduction, depending on the results of ∙O₂^- radicals and defect measurement by electron spin resonance, X-ray photoelectron spectroscopy, atmosphere-controlled surface photovoltage spectra, etc. This work provides an easy and efficient strategy for the preparation of high-performance solar-driven TiO₂ photocatalysts.