One-step topological preparation of carbon doped and coated TiO2 hollow nanocubes for synergistically enhanced visible photodegradation activity

Abstract

Various three-dimensional TiO₂ hollow structures have attracted strong scientific and technological attention due to their excellent properties. 3D hierarchical TiO₂ hollow nanocubes (TiO₂-HNBs) are not good candidates for industrial photocatalytic applications due to their large energy gap which is only activated by UV light. Herein, visible-light-responsive carbon doped and coated TiO₂-HNBs (C@TiO₂-HNBs) with a dominant exposure of {001} facets have been prepared via a template-engaged topotactic transformation process using facile one-step solvothermal treatment and a solution containing ethanol, glucose and TiOF₂. The effects of reaction time and glucose/TiOF₂ mass ratio on the structure and performance of C@TiO₂-HNBs were systematically studied. We found that glucose played an important role in providing H₂O during the topological transformation from self-templated TiOF₂ cubes into 3D hierarchical TiO₂ hollow nanocubes versus dehydration reactions, where its main function was as a carbon source. Coated carbon was deposited predominantly on the surface as sp² graphitic carbon in extended p conjugated graphite-like environments, and doped carbon mainly replaced Ti atoms in the surface lattice to form a carbonate structure. The results were confirmed using TEM SEM, EDS, XRD, FT-IR, XPS and Raman spectroscopic studies. The C@TiO₂-HNBs achieved greatly improved RhB photodegradation activity under visible light irradiation. The catalyst prepared with glucose/TiOF₂ at a mass ratio of 0.15 (T24-0.15) showed the highest photodegradation rate of 96% in 40 min, which is 7.0 times higher than those of the TiO₂-HNBs and P25. This new synthetic approach proposes a novel way to construct carbon hybridized 3D hierarchical TiO₂ hollow nanocubes by combining two modification methods, “element doped” and “surface sensitized”, at the same time.