Degradation of azo dye under visible light irradiation over nanographene oxide–zinc oxide nanocomposite as catalyst

Abstract

Nanographene oxide (NGO) was prepared from natural graphite flakes via modified Hummer’s method. Nanocomposite of NGO and zinc oxide (NGO–ZnO) in the ratio of 1:1 was prepared by sol–gel method. Structural and physiochemical properties of the synthesized NGO and NGO–ZnO nanocomposite were investigated with the help of powder X ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope coupled with energy-dispersive X ray analysis (SEM/EDX), thermal gravimetric analysis and differential scanning calorimetry (TGA/DSC) and atomic force microscopy (AFM). The PXRD results showed the conversion of graphite to nanographene oxide. It was observed from the FTIR spectra that graphite oxidized by strong oxidant KMnO4 showed the presence of oxygen atoms on the graphite layer. Thus, certifies the presence of oxygen-containing functional groups COOH, C=O, C–O–C in GO films. SEM image indicated the morphology of NGO and inclusion of nano-zinc oxide in graphene layer. EDS analyzed the components in the material. Percentage of oxygen in NGO shows extensive oxidation of graphene layer and percentage of zinc calculated by EDS agreed with theoretical ratio. TGA/DSC analyzer indicated the thermal stability of the material. AFM indicated exfoliation of graphite to graphene. Photocatalytic activities of the prepared samples were evaluated by degradation of rhodamine 6B (Rh 6B) azo dye in aqueous solution. From the measured absorbance values, the photocatalytic activity of NGO–ZnO nanocomposite was found to be excellent than pure NGO.