Enhanced visible photocatalytic activity of TiO2 hollow boxes modified by methionine for RhB degradation and NO oxidation

Hierarchical TiO2 hollow nanoboxes (TiO2-HNBs) assembled from TiO2 nanosheets (TiO2-NSs) show improved photoreactivity when compared with the building blocks of discrete TiO2-NSs. However, TiO2-HNBs can only be excited by ultraviolet light. In this paper, visible-light-responsive N and S co-doped TiO2-HNBs were prepared by calcining the mixture of cubic TiOF2 and methionine (C5H11NO2S), a N- and S-containing biomacromolecule. The effect of calcination temperature on the structure and performance of the TiO2-HNBs was systematically studied. It was found that methionine can prevent TiOF2-to-anatase TiO2 phase transformation. Both N and S elements are doped into the lattice of TiO2-HNBs when the mixture of TiOF2 and methionine undergoes calcination at 400 degrees C, which is responsible for the visible-light response. When compared with that of pure 400 degrees C-calcined TiO2-HNBs (T400), the photoreactivity of 400 degrees C-calcined methionine-modified TiO2-HNBs (TM400) improves 1.53 times in photocatalytic degradation of rhodamine-B dye under visible irradiation (lambda > 420 nm). The enhanced visible photoreactivity of methionine-modified TiO2-HNBs is also confirmed by photocatalytic oxidation of NO. The successful doping of N and S elements into the lattice of TiO2-HNBs, resulting in the improved light-harvesting ability and efficient separation of photo-generated electron-hole pairs, is responsible for the enhanced visible photocatalytic activity of methionine-modified TiO2-HNBs. The photoreactivity of methionine modified TiO2-HNBs remains nearly unchanged even after being recycled five times, indicating its promising use in practical applications. (C) 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.