Construction of an S-scheme TiOF2/HTiOF3 heterostructures with abundant OVs and O-H groups: Performance, kinetics and mechanism insight

Developing efficient photocatalysts is of crucial significance for the development of photocatalysis tech-niques. In this work, an S-scheme alkaline-washed TiOF2/HTiOF3(OHTOF) heterostructures with abun-dant Oxygen vacancies (Ovs) and O-H groups was successfully constructed and used to remedy antibiotic wastewater under simulated sunlight. The generation of HTiOF3 was induced by g-C3N4 regu-lation. The results displayed that OHTOF15 composite possessed the best photocatalytic performance, which could degrade 94.2% tetracycline hydrochloride (TCH) at a rate speed constant of 1.077 min -1 in 2.5 h. The after-alkali-washing process increased the concentration of O-H groups and Ovs defects, and greatly enlarged the surface area. The abundant Ovs and O-H groups were conducive to the forma-tion of free radicals' and the transport of charge carriers. Compared with the pristine TiOF2, the absorp-tion sidebands of OHTOF series were greatly red-shifted, which indicated that the increase of O-H groups and the etching of the morphology of OHTOF further enhanced its visible-light harvesting ability. Furthermore, the metal cycle of the variable state of Ti4./Ti3. in OHTOF15 compensated for the charge balance and promoted the efficient separation of the carriers. Additionally, the apparent quantum effi-ciency (AQE) of the TCH photodegradation system based on Chemical Oxygen Demand (COD) removal efficiency was calculated to be 0.32%. It was confirmed that the electron transport path in TiOF2/ HTiOF3 nanocomposites system followed the S-scheme type, which increased the charge carriers' sepa-ration rate and maintained a strong redox capacity. This work could provide some enlightenment for the construction of the semiconducting heterojunction and controllable surface defects engineering. (c) 2023 Elsevier Inc. All rights reserved.