Visible-Light-Induced Self-Cleaning Property of Bi₂Ti₂O₇‑TiO₂ Composite Nanowire\nArrays

Abstract

Bi₂Ti₂O₇-TiO₂ composite nanowire\narrays were prepared via a two-step sequential solvothermal and subsequent\ncalcination process. The morphology and structure of the Bi₂Ti₂O₇-TiO₂ composite nanowire array\ncomposite were characterized by X-ray diffraction, field emission\nscanning electron microscopy, and transmission electron microscopy.\nThe UV–visible diffuse reflectance spectroscopy analysis indicated\nthat the absorption spectrum of the Bi₂Ti₂O₇-TiO₂ composite nanowire array composite was extended\nto the visible-light region due to the existence of Bi₂Ti₂O₇. The Bi₂Ti₂O₇-TiO₂ composite nanowire arrays exhibit superhydrophilicity\nwith water contact angles of 0° after irradiation with visible\nlight, and the superhydrophilic nature is retained for at least 15\ndays. This effect enables us to consider self-cleaning applications\nthat do not require permanent UV exposure. Compared to pure Bi₂Ti₂O₇ and TiO₂, the vertically\naligned Bi₂Ti₂O₇-TiO₂ composite\nnanowire arrays showed more significant visible-light self-cleaning\nperformance due to the synergistic effect of superhydrophilicity and\nsignificant photocatalytic activity caused by effective electron–hole\nseparation at the interfaces of the two semiconductors, which was\nconfirmed by the electrochemical analysis and surface photovoltage\ntechnique.