Ultrasound assisted preparation of rGO/TiO2 nanocomposite for effective photocatalytic degradation of methylene blue under sunlight

Abstract

In the present work, well known Hummers–Offeman method was employed for production of graphene oxide (GO) and in-situ deposition of TiO2 nanoparticles on prepared GO in presence of ultrasonic irradiations to get reduced graphene oxide-TiO2 (rGO/TiO2) nanocomposite. The structural and morphological analysis of synthesized photocatalysts was accomplished with UV–Vis, XRD, FT-IR, Raman Spectra, EDAX, XPS and TEM analysis. The absorption peak at 234 nm shows redshift to 285 nm which confirms the reduction of GO to rGO. XRD analysis of the prepared composite confirmed the presence of the combination of anatase and rutile phases of TiO2. TEM images revealed that large amount of round-shaped TiO2 nanoparticles in size range of 3 to 5 nm were consistently deposited on the rGO sheet due to ultrasonic irradiations. Further, effectiveness of the prepared nanocomposite as a photocatalyst was examined with the decolourization of methylene blue (MB) dye in sun light. The effect of catalyst loading and pH on MB dye degradation was examined. The results indicated that the percent degradation of selected MB dye enhanced at higher catalyst loading and also a higher pH favoured the degradation. The maximum MB dye degradation was observed to be 91.3% within 30 min for pH value of 13.2 and photocatalyst dosage of 2 g/L. Further, the kinetic studies established the pseudo first-order reaction kinetics for the photocatalytic decolourization/degradation of MB dye.