Abstract
This study presents a novel method for the development of TiO2/reduced graphene oxide (rGO) nanocomposites for photocatalytic degradation of dyes in an aqueous solution. The synergistic integration of rGO and TiO2, through the formation of Ti–O–C bonds, offers an interesting opportunity to design photocatalyst nanocomposite materials with the maximum absorption shift to the visible region of the spectra, where photodegradation can be activated not only with UV but also with the visible part of natural solar irradiation. TiO2@rGO nanocomposites with different content of rGO have been self-assembled by the hydrothermal method followed by calcination treatment. The morphological and structural analysis of the synthesized photocatalysts was performed by FTIR, XRD, XPS, UV-Vis DRS, SEM/EDX, and Raman spectroscopy. The effectiveness of the synthesized nanocomposites as photocatalysts was examined through the photodegradation of methylene blue (MB) and rhodamine B (RhB) dye under artificial solar-like radiation. The influence of rGO concentration (5 and 15 wt.%) on TiO2 performance for photodegradation of the different dyes was monitored by UV-Vis spectroscopy. The obtained results showed that the synthesized TiO2@rGO nanocomposites significantly increased the decomposition of RhB and MB compared to the synthesized TiO2 photocatalyst. Furthermore, TiO2@rGO nanocomposite with high contents of rGO (15 wt.%) presented an improved performance in photodegradation of MB (98.1%) and RhB (99.8%) after 120 min of exposition to solar-like radiation. These results could be mainly attributed to the decrease of the bandgap of synthesized TiO2@rGO nanocomposites with the increased contents of rGO. Energy gap (Eg) values of nanocomposites are 2.71 eV and 3.03 eV, when pure TiO2 particles have 3.15 eV. These results show the potential of graphene-based TiO2 nanocomposite to be explored as a highly efficient solar light-driven photocatalyst for water purification.
Highlights
Nowadays, accessible clean water and energy resources are among the highest priorities for sustainable economic growth and societal wellbeing
The successful preparation of materials by the combination of the hydrothermal method and calcination can be demonstrated with detailed characterization of the obtained
The Graphene oxide (GO) spectrum present the following peaks at 3372 cm−1 corresponded to the stretching vibration of the carboxyl group (−OH), which was ascribed on the attendance of alcohol groups and absorbed water molecules, 2857 cm−1 and 2925 cm−1 vibrations corresponded to the symmetric and asymmetric CH2 stretching of GO [34,35]
Summary
Accessible clean water and energy resources are among the highest priorities for sustainable economic growth and societal wellbeing. Research activities focus on the synthesis of new materials for use in energy-efficient processes for water treatment by using doped metal oxides with a reduced bandgap, which allows photocatalysis in the visible region of the electromagnetic spectrum [1,2]. Different types of pollutants such as pharmaceuticals, dyes, pesticides, etc., are widespread and may interact with the environment through different pathways. As relevant environmental pollutants, methylene blue (MB) dye and rhodamine B (RhB) dye were selected as complex compounds for decomposition from an aqueous medium because of their often-frequent occurrence in the environment. MB and RhB are widely utilized for industrial production purposes such as dyeing and printing on textile, leathers, papers, and on plastics [3,4,5]
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