Photocatalytic Molecular Oxygen Activation Over Single‐Atom Fe Decorated {001}‐Faceted TiO 2 Nanosheets for Formaldehyde Degradation

ABSTRACT This study systematically investigated the catalytic oxidation performance of single‐atom iron (Fe)‐doped titanium dioxide (Fe/TiO 2 ) photocatalysts toward gaseous formaldehyde (HCHO) under visible light irradiation. The experimental results demonstrated that the incorporation of single‐atom Fe significantly enhanced the photocatalytic activity, attaining a 99.05% HCHO removal rate (residual concentration of 0.43 ppm after 1 h), outperforming most TiO 2 ‐based materials. The fundamental enhancement mechanism was elucidated using in situ DRIFTS spectroscopy, EPR, TOF‐SIMS, and DFT calculations. The results revealed that single Fe atoms and oxygen vacancies serve as active sites and electron reservoirs, thereby enhancing molecular oxygen activation by promoting electron transfer to the π‐antibonding orbital (π 2p * ) of O 2 . Consequently, this process generated highly reactive monoatomic oxygen anions (O − ) as the dominant reactive oxygen species. Further mechanistic analysis has confirmed that the O − species can oxidize HCHO through a DOM intermediate pathway, ultimately mineralizing it into CO 2 and H 2 O. This study elucidated the pivotal role of O − radicals in the deep oxidation of HCHO and provided novel theoretical insights and strategic guidance for the design of highly efficient TiO 2 ‐based air‐purification materials.