Facile and Green Fabrication of Microwave-Assisted Reduced Graphene Oxide/Titanium Dioxide Nanocomposites as Photocatalysts for Rhodamine 6G Degradation.

Organic pollutants, such as synthetic dyes, are treated to prevent them from contaminating natural water sources. One of the treatment methods is advanced oxidation process using a photocatalyst material as the active agent. However, many photocatalysts are hindered by their production cost and efficiency. In this study, nanocomposites consisting of reduced graphene oxide and titanium dioxide (rGO/TiO) were prepared by a simple and green approach using the microwave-assisted method, and we utilized a graphene oxide (GO) precursor that was fabricated through the Tour method. The ratios of rGO/TiO in nanocomposites were varied (2:1, 1:1, and 1:2) to know the influence of rGO on the photocatalytic performance of the nanocomposites for rhodamine 6G degradation. Transmission electron microscopy (TEM) observation revealed that a transparent particle with a sheetlike morphology was detected in the rGO sample, suggesting that a very thin film of a few layers of GO or rGO was successfully formed. Based on scanning electron microscopy (SEM) observation, the rGO/TiO nanocomposites had a wrinkled and layered rGO structure decorated by TiO nanoparticles with average diameters of 125.9 ± 40.6 nm, implying that rGO layers are able to prevent TiO from agglomeration. The synthesized product contained only rGO and TiO in the anatase form without impurities that were proven by Raman spectra and X-ray diffraction (XRD). The nanocomposite with rGO/TiO ratio 1:2 (composite C) was found to be the best composition in this study, and it was able to degrade 82.9 ± 2.4% of the rhodamine 6G after UV irradiation for 4 h. Based on a time-resolved photoluminescence study at wavelength emission 500 nm, the average decay lifetime of R6G-rGO/TiO composites (2.91 ns) was found to be longer than that of the R6G-TiO sample (2.05 ns), implying that the presence of rGO in rGO/TiO composites successfully suppressed the electron-hole recombination process in TiO and significantly improved their photocatalytic performance. This study showed that the rGO/TiO nanocomposites synthesized through relatively simple and eco-friendly processes display promising prospects for photocatalytic degradation of dyes and other recalcitrant pollutants in a water stream.