Confined growth of oxygen-vacancy rich TiO2-x nanoparticles with heterophase junction for high-efficiency photocatalytic water purification

Photocatalysis stands out as a promising technique for waste purification, but its practical application is limited by the insufficient generation of reactive oxygen species (ROS) over photocatalyst. Herein, we proposed a dual strategy for promoting ROS generation by the construction of oxygen-vacancy-rich TiO2-x confined on silica nanosheet (TiO2-x@S-A500). The surface-confinement effect arising from silica lead to the formation of TiO2 anatase/brookite heterophase junctions, thus enhancing the photogenerated charge separation. More importantly, the oxygen vacancies (Vo) introduced by silica-mediated reaction were spatially confined at the interface between silica and TiO2, which served as trap centers to capture photogenerated electrons, thus facilitating the O2 activation for generations of •O2– and 1O2. Eventually, TiO2-x@S-A500 exhibited enhanced photocatalytic performance for degrading phenolic pollutants under sunlight irradiation, with the degradation rate constant (k) for 4-chlorophenol that was 2.4 and 3 times higher than that of pure TiO2 and P25, respectively, and the toxicities for its intermediates were greatly reduced. Additionally, 180 mg/L of COD present in the real biologically pretreated coal gasification wastewater was degraded within 60 min to 45 mg/L, satisfying the Integrated Wastewater Discharge Standard of China.