Heterojunction of graphene and titanium dioxide nanotube composites for enhancing photocatalytic activity

Herein we studied the structure deformation and photoluminescence properties of titanium dioxide nanotube (TNT) hydrothermally grown on pristine graphene (Gr) surfaces. This Gr/TNT composite shows photocatalytic enhancement in terms of methylene blue degradation efficiency and short saturation time, as a result of heterogeneous junction formation through the interfacial connection of graphene by a facile one-step hydrothermal method. The Gr content within the composites was varied between 0.5 wt.%-8 wt.%, and the sample containing 5 wt% Gr (0.01 g) displayed the highest photocatalytic activity with methylene blue (20 ppm) degradation efficiency of 99.63%. In addition, all the composites exhibited a very short saturation time of ~5 min under sunlight irradiation. The morphological, crystal structural, optical and photocatalytic properties of the composite material were investigated using transmission electron microscopy, scanning electron microscopy, x-ray diffraction, Raman scattering spectroscopy and photoluminescence spectroscopy. The TNTs grown in situ with graphene showed that it enhanced their photocatalytic activity via the reduced carrier recombination rate of TNTs, which was studied by photoluminescence emission measurement. Furthermore, the mechanism by which the combined material properties affect the photocatalytic performance were characterized and clarified.