Abstract
In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradation efficiencies when compared to those obtained with not doped TiO2.
Highlights
Since the discovery by Fujishima and Honda of the photochemical water splitting in presence ofTiO2 [1], heterogeneous photocatalysis has been widely studied for its environmental applications [2,3].Many compounds present in effluents are not degradable by traditional biological and physical methods, and TiO2 photocatalysis represent a new technology to treat and remove these compounds in wastewaters [4,5]
TiO2 is a semiconductor material characterized by an electronic band structure in which the lowest occupied energy band, the valence band (VB), and the highest empty band, the conduction band (CB), are separated by a band gap
When TiO2 is irradiated by UV light with energy greater than its band gap, an electron from the VB is promoted to the CB living a hole in the VB
Summary
Since the discovery by Fujishima and Honda of the photochemical water splitting in presence ofTiO2 [1], heterogeneous photocatalysis has been widely studied for its environmental applications [2,3].Many compounds present in effluents are not degradable by traditional biological and physical methods, and TiO2 photocatalysis represent a new technology to treat and remove these compounds in wastewaters [4,5]. TiO2 has received considerable attention for various applications such as solar energy conversion [6,7] and environmental photocatalysis [8,9]. This is due to the features of this semiconductor, such as its high efficiency for the decomposition of organic pollutants, its non-toxicity, its biological and chemical inertness, its photochemical stability, its low cost and its transparency to visible light [10]. When TiO2 is irradiated by UV light with energy greater than its band gap, an electron from the VB is promoted to the CB living a hole in the VB. These electron-hole pairs allow the formation of active species such as hydroxyl radicals and Catalysts 2018, 8, 598; doi:10.3390/catal8120598 www.mdpi.com/journal/catalysts
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