Ti powder-assisted synthesis of Ti3+ self-doped TiO2 nanosheets with enhanced visible-light photoactivity

Abstract

TiO₂ nanocrystals with exposed high-energy (001) facets have been reported to show higher photocatalytic activity than those with exposed traditional (101) facets. However, they can only be excited by UV light. In this paper, visible-light responsive Ti³⁺-doped TiO₂ nanosheets with exposed (001) facets were one-pot fabricated by hydrothermal treatment of a mixture solution of tetrabutyl titanate (80 mmol) and hydrofluoric acid (80 mmol) in the presence of Ti powder (0–12 mmol) at 200 °C for 24 h. The prepared Ti³⁺-doped TiO₂ nanosheet photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption–desorption isotherms. The photocatalytic activity was evaluated by a photoluminescence (PL) technique using coumarin as a probe molecule under visible-light irradiation. The experimental results show that the visible-light photocatalytic activity of the prepared photocatalyst increases first and then decreases with increasing amount of Ti powder. Ti³⁺–TiO₂ nanosheets prepared in the presence of 4 mmol Ti powder show the highest visible-light photoactivity.