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.
Titanate nanotubes were prepared by hydrothermal synthesis, followed by Titanate nanotubes were prepared by hydrothermal synthesis, followed by proton exchange, and calcined at 250°C for 2h. The properties of prepared nanotubes were investigated with field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), adsorption-desorption N 2 isotherms and UV-Vis diffuse reflectance spectroscopy (DRS). As-prepared sample displayed strongly aggregated nanotubes with crystal structure of H 2 Ti 2 O 5 ×H 2 O. Calcination yielded with loss of interlayer water and partial transformation of nanotubes to anatase phase. Adsorption and photocatalytic decomposition of methylene blue, used as a model pollutant, on as-prepared and calcined titanate nanotubes have been studied. It was established that calcination at 250°C for 2h improves the adsorption and photocatalytic properties of titanate nanotubes. It was shown that pseudo-second-order model was the most appropriate to describe adsorption of methylene blue on titanate nanotubes. Affinity toward methylene blue of 48.45mg g-1 and 95.24mg g-1 has been established for as-prepared and calcined titanate nanotubes, while equilibrium adsorption was attained in 120min. Adsorption process is controlled by intraparticle diffusion and surface sorption in both samples, but the contribution of surface sorption is greater for the calcined sample. The pseudo-first-order kinetic is an acceptable model for photocatalytic dye degradation process on titanate nanotubes. It was shown that the calcination slightly increased the photocatalytic activity of titanate nanotubes.
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