Enhanced photocatalytic activity of graphene oxide decorated on TiO< sub> 2 films under UV and visible irradiation (original) (raw)
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Current Applied Physics, 2011
Novel grapheneeTiO 2 (GReTiO 2 ) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO 2 nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO 2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using grapheneeTiO 2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GReTiO 2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO 2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant p-conjugation system and two-dimensional planar structure of graphene.
Enhanced photocatalytic activity of graphene–TiO2 composite under visible light irradiation
Current Applied Physics, 2013
Novel grapheneeTiO 2 (GReTiO 2 ) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO 2 nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO 2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using grapheneeTiO 2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GReTiO 2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO 2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant p-conjugation system and two-dimensional planar structure of graphene.
Effect of graphene thickness on photocatalytic activity of TiO 2 -graphene nanocomposites
Reduced graphene oxide sheets (RGO) with different number of graphene layers were used as platforms for TiO 2 nanoparticles deposited using hydrothermal process. The nanomaterials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and diffuse reflectance UV–vis spectroscopy (DR-UV-vis). The photocatalytic activity of the nanocomposites was investigated in a model reaction of phenol decomposition under visible light irradiation. Here, the influence of graphene thickness on its photoactivity was explored. It was found that the highest photocatalytic activity was observed for the catalyst composed of single layer graphene and decreased when a number of graphene layers was higher. This might be related to the surface and electronic properties of reduced graphene oxide arising from different number of graphene layers and its interaction with titanium dioxide: (i) higher interfacial area of TiO 2-RGO with lower thickness of RGO, which could influence in enhanced transferring of photoinduced electron–hole pairs between TiO 2 and RGO, hence improving their separation ; (ii) variations in excitations lifetime relating to the diverse surface quality and density of trap sites of reduced graphene oxide; (iii) higher charge carriers mobility in 1-layer RGO compared to 2-and few-layers.
Catalysts
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 photodegradati...
Physical Chemistry Chemical Physics, 2013
Model photocatalysts composed of TiO 2 -graphene nanocomposites are prepared to address the effect of graphene quality on their photocatalytic performance. Graphene is synthesized by catalyst-assisted chemical vapor deposition (CVD), catalyst-free CVD and solution processing methods. TiO 2 is prepared by reactive magnetron sputtering and subsequent annealing. Fabricated model photocatalysts have different morphology and physical properties, as revealed using spectrophotometry, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence, and four-probe electrical measurements. All graphene-containing composites have significantly higher photocatalytic activity compared to bare TiO 2 films in the gas phase methanol photooxidation tests. Their activity is proportional to the electrical conductivity and surface roughness of the respective carbon structure, which in turn depends on the preparation methods. The mechanisms of enhancement are further assessed by comparison with the performance of reference TiO 2 -graphitic-carbon and TiO 2 -Au thin films.
Applied Sciences
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 artificia...
Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide
arXiv: Materials Science, 2018
Graphene, a two-dimensional (2D) promising emergent photocatalyst consisting of earth-abundant elements. This study evaluated the potential of graphene oxide (GO) towards photocatalytic degradation of a novel organic dye, Methylene Blue (MB). In this work, photocatalytic activity of graphene oxide (GO), graphene oxide (GO) along with hydrogen peroxide (H2O2) were tested by photodegrading Methylene Blue (MB) in aqueous solution. The resulted GO nanoparticles were characterized by X-ray powder diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Ray Spectroscopy. The XRD data confirms the sharp peak centered at 2Theta=10.44 degree corresponding to (002) reflection of GO. Based on our results, it was found that the resulted GO nanoparticles along with H2O2 achieved ~92% photodecolorization of MB compared to ~63% for H2O2 under natural sunlight irradiation at pH~7 in 60 min. The influences of oxygen and hydrogen peroxide (H2O2) on the ...
Catalysts, 2017
Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO 2 is one of the most widely studied and used photocatalysts for environmental remediation. However, it is mainly active under UV-light irradiation due to its band gap of 3.2 eV, while it shows low efficiency under the visible light spectrum. Regarding the exploration of TiO 2 activation in the visible light region of the total solar spectrum, the incorporation of carbon nanomaterials, such as graphene, in order to form carbon-TiO 2 composites is a promising area. Graphene, in fact, has a large surface area which makes it a good adsorbent for organic pollutants removal through the combination of electrostatic attraction and π-π interaction. Furthermore, it has a high electron mobility and therefore it reduces the electron-hole pair recombination, improving the photocatalytic activity of the semiconductor. In recent years, there was an increasing interest in the preparation of graphene-based TiO 2 photocatalysts. The present short review describes the recent advances in TiO 2 photocatalyst coupling with graphene materials with the aim of extending the light absorption of TiO 2 from UV wavelengths into the visible region, focusing on recent progress in the design and applications in the photocatalytic degradation of synthetic dyes.
Structure and photocatalytic properties of TiO2-Graphene Oxide intercalated composite
Chinese Science Bulletin, 2011
TiO2-Graphene Oxide intercalated composite (TiO2-Graphene Oxide) has been successfully prepared at low temperature (80°C) with graphite oxide (GO) and titanium sulfate (Ti(SO4)2) as initial reactants. GO was firstly exfoliated by NaOH and formed single and multi-layered graphite oxide mixture which can be defined as graphene oxide, [TiO]2+ induced by the hydrolysis of Ti(SO4)2 diffused into graphene oxide interlayer by electrostatic
Applied Catalysis B: Environmental, 2012
Reduced graphene oxide-TiO 2 composites (GOT) were prepared by liquid phase deposition followed by post-thermal reduction at different temperatures. The composite materials were systematically evaluated as photocatalysts for the degradation of an important pharmaceutical water pollutant, diphenhydramine (DP), and an azo-dye, methyl orange (MO), under both near-UV/Vis and visible light irradiation as a function of the graphene oxide (GO) content. A marked compositional dependence of the photocatalytic activity was evidenced for DP and MO pollutants degradation and mineralization under both UV/Vis and visible light. Especially under visible light, optimum photocatalytic performance was obtained for the composites treated at 200 • C comprising 3.3-4.0 wt.% GO, exceeding that of the benchmark P25 (Evonik) catalyst. According to scanning electron microscopy, Raman spectroscopy, and porosimetry analysis data, this was attributed to the optimal assembly and interfacial coupling between the reduced GO sheets and TiO 2 nanoparticles. Almost total degradation and significant mineralization of DP and MO pollutants (in less than 60 min) was achieved under near-UV/Vis irradiation for the optimum GOT composites. However, higher GO content and calcination temperatures (350 • C) led to detrimental effects due to the GO excess and the disruption of the GO-TiO 2 binding. Photocatalytic experiments employing sacrificial hole and radical scavenging agents revealed that photogenerated holes are the primary active species in DP degradation for both bare TiO 2 and GOT under UV/Vis irradiation, while an enhanced contribution of radical mediated DP oxidation was evidenced under visible light. These results combined with the distinct quenching of the GO photoluminescence under visible and NIR laser excitation, indicate that reduced GO acts either as electron acceptor or electron donor (sensitizer) of TiO 2 under UV and visible light, respectively. Fine-tuning of the reduced GO-TiO 2 interface is concluded as a very promising route to alleviate electron-hole recombination and circumvent the inherently poor light harvesting ability of TiO 2 in the visible range.