TiO 2 /graphene and TiO 2 /graphene oxide nanocomposites for photocatalytic applications: A computer modeling and experimental study

Abstract

This work reports a computational study, focused on graphene (G) and graphene oxide (GO) interfaces with titanium dioxide (TiO 2), and an experimental assay on the photocatalytic activity of TiO 2 /G and TiO 2 /GO nanocomposites in the degradation of two different pollutants: methylene blue and ciprofloxacin. Both carbon nanostructures were compared due to their different chemical structure: GO is a G derivative with oxygen functional groups which should promote a closer chemical interaction with TiO 2 nanoparticles. Computational models of the fundamental properties of the composites indicated potentially improved photocatalytic activity compared to TiO 2 , namely lower band gaps and charge carrier segregation at the interfaces. These fundamental properties match qualitatively experimental results on methylene blue, which was more effectively degraded by TiO 2 /G and TiO 2 /GO nanocomposites than by pure TiO 2 under UV light. In contrast, the same nanocomposites were found to be less efficient to degrade ciprofloxacin than pure TiO 2 under visible and UV light. Therefore, this work showcases the relevance of an efficient matching between the catalyst and the molecular properties and structure of the pollutant.

Recent Advancements in the Understanding of the Surface Chemistry in TiO2 Photocatalysis

“…Figure 9 shows the structure of anatase-GR and anatase-GO interfaces. Experimentally, it was found that GR and GO loading can decrease the anatase band gap [95]. This decrease can be related to the formation of additional states associated with the interaction of TiO2 and graphene.…”

TiO2-reduced graphene oxide nanocomposites for the trace removal of diclofenac

“…The band gap of T-RGO5 is calculated to be about 2.75 eV which is smaller than the 3.25 eV of TiO 2 . The narrowing of band gap due to the existence of additional C2p mid energy levels of graphene between O2p and Ti3d states of TiO 2 is already established [12,26].…”

“…It also shows a broad peak at around 3400 cm −1 , which are due to the O−H stretching vibrations of surface hydroxyl groups. The peak at 1635 cm −1 originates from the stretching vibrations of hydroxyl groups of adsorbed molecular water [12]. In the spectrum of RGO, the peak appearing at 1600 cm −1 is ascribed to the skeletal vibration of RGO sheet [16].…”

“…The integration of TiO 2 with graphene promotes enhanced light absorption in the visible region, good adsorptivity and excellent mobility of charge carriers which could improve photodegradation of pollutants. However, the evaluation of photocatalytic performance of TiO 2 -graphene nanocomposites has been limited towards certain types of compounds such as dyes [12], volatile organic compounds in gas phase [13] and reduction of Cr(VI) [14]. Only very few studies are reported on the effectiveness of the catalyst for the removal of emerging micro pollutants like pharmaceuticals [15,16] from water.…”

Pyrolytic Formation of TiO2/Carbon Nanocomposite from Kraft Lignin: Characterization and Photoactivities

“…An examination of the photocatalytic activity of the nanocomposite in the degradation of RhB in aqueous media under solar light irradiation for 60 min revealed a removal of 98% as compared with pure TiO 2 (42%), graphite oxide (19%) and a mechanical mixture of graphene and TiO 2 (60%) owing to increased light absorption and reduced electron-hole pair recombination upon intercalation of graphene and TiO 2 . A wide-ranging work enclosing a computational study focused on the titania-graphene (TiO 2 /G) nanocomposite interface and on its photocatalytic performance on MB degradation using different quantities of G on P25 TiO 2 has been carried out by Martins et al [33]. Experimental results revealed that the nanocomposite TiO 2 /G (3.0% in graphene) degraded MB more efficiently (0.160 min −1 ) than TiO 2 alone (0.070 min −1 ).…”