Facet engineered TiO2 hollow sphere for the visible-light-mediated degradation of antibiotics via ligand-to-metal charge transfer

Efficient removal of tetracycline (TC) under visible-light irradiation over TiO2 -based photocatalysts remains a challenge based on the fact that the reported photocatalytic systems still suffer from weak visible-light absorption and/or inefficient charge separation. Herein, we constructed {101} and {001} facets co-exposed TiO2 hollow sphere (001-HT) via a gentle NaF treatment, in which the hollow mesoporous feature can trap incident light for a long time to improve photons efficiently. Meanwhile, the as-formed facet heterojunction significantly facilitates the charge separation. As a result, the 001-HT exhibits a high removal rate (similar to 90.1%) of TC under visible-light irradiation, beyond the values of many reported TiO2 -based photocatalysts. Most importantly, we further expound the ligand-to-metal charge transfer mechanism towards TiO2 -assisted degradation of TC under visible-light irradiation, which effectively clarifies the confusion about the origin of pure TiO2 visible-light activity towards TC degradation because both TiO2 and TC do not exhibit any visible-light catalytic activity. Therefore, this work provides a new insight in revealing the mechanism of visible-light-mediated TC degradation over pure TiO2 photocatalyst.