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In this study, ZnO/reduced graphene oxide (ZnO/rGO) nanocomposites with various GO concentrations were hydrothermally fabricated. We showed that ZnO and rGO phases coexist in these ZnO/rGO nanocomposites and that the ZnO morphology varies from nanoplates to nanoparticles, with the average ZnO nanocrystal decreasing in size from 38 nm to 20 nm as the GO concentration increased from 0% to 10%. Oxygen-containing functional groups were strongly reduced during the ZnO/GO hybridization process used to form these nanocomposites. The visible 400–800 nm absorption band of the rGO layers increased in intensity with increasing GO concentration. Photocatalytic activity of ZnO/rGO nanocomposite samples was studied under visible light for 60 min. The photocatalytic properties of the ZnO/rGO nanocomposites were significantly superior to those of pure ZnO, with photocatalytic efficiency increasing with increasing GO concentration. Photocatalytic efficiency of ZnO/rGO nanocomposites increased by 30%, 32%, and 60% for samples with 4%, 6%, and 10% GO concentration respectively, after 60 min. These results highlight the potential of the ZnO/rGO nanocomposites for use in pollution-remediation applications.

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.