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

ABSTRACT

Developing efficient photocatalysts is of crucial significance for the development of photocatalysis techniques. In this work, an S-scheme alkaline-washed TiOF2/HTiOF3(OHTOF) heterostructures with abundant Oxygen vacancies (Ovs) and OH groups was successfully constructed and used to remedy antibiotic wastewater under simulated sunlight. The generation of HTiOF3 was induced by g-C3N4 regulation. The results displayed that OHTOF15 composite possessed the best photocatalytic performance, which could degrade 94.2% tetracyclinehydrochloride (TCH) at a rate speed constant of 1.077 min-1 in 2.5 h. The after-alkali-washing process increased the concentration of OH groups and Ovs defects, and greatly enlarged the surface area. The abundant Ovs and OH groups were conducive to the formation of free radicals' and the transport of charge carriers. Compared with the pristine TiOF2, the absorption sidebands of OHTOF series were greatly red-shifted, which indicated that the increase of OH 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 efficiency (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' separation 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.