Oxygen vacancy/Ti3+ engineered TiO2 nanotube arrays prepared by in-situ exfoliation with H2 bubbles: A visible-light-driven self-supporting photocatalyst for detoxfication of chloraphenicol

Abstract

Oxygen vacancy/Ti3+ engineered TiO2 nanotube arrays were prepared through electrochemical strategy at high potential (−6 V). The electrons surging from DC power initiate the valance decline of Ti4+, and countless H2 bubbles released from TiO2 surface lead to the in-situ exfoliation of some TiO2 tiny debris, generating point defects containing Ti3+ inside the TiO2 and oxygen vacancy (OV) embedded on TiO2. The generated Ti3+/ OV help TiO2 to increase the harvest toward visible light and serve as active sites for activating molecular oxygen to form superoxide radical (·O2-). Besides, as improved separation of electron-hole pairs endowed by the defects, the yield of hydroxyl radicals (·OH) is enhanced compared with the pristine TiO2. Chloramphenicol (CAP, an antibiotic) molecules can be efficiently degraded with the reduced TiO2 under the visible light with its degradation and evolution pathway expounded in detail. Fukui index is employed to anticipate the probable sites that are subjected to oxidation by·OH and the MS spectra evidence that the·OH governs the decomposition routes of CAP molecules. ECOSAR simulation evaluates the toxicity of CAP and the intermediates, demonstrating that the final products from the photocatalysis do not post any hazardous risk on ecosystem.