Synthesis, characterization and photocatalystic activity of multiwalled carbon nanotubes/titanium dioxide nanocomposite (original) (raw)
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physica status solidi (b), 2011
With different mass ratios, titanium dioxide/carbon nanotube (0.1-10 wt% CNT content) nanocomposites were prepared with the aid of ultrasonication method. The structures of the various TiO 2 /CNT nanocomposites were characterized by electron microscopy (scanning electron microscopy, transmission electron microscopy). Their photocatalytic activity was tested by the degradation of phenol in aqueous solution under near-UV irradiation. In parallel experiments, both (SW and MW) CNT samples were treated in a reflux system with nitric acid to functionalize the nanotubes, subsequently preparing the nanocomposites in the same method. At higher CNT concentration (5, 10 wt%) the nanocomposites exhibited lower photocatalytic ß
Enhancement of photocatalytic activity of mesoporous TiO2 by using carbon nanotubes
Applied Catalysis A: General, 2005
Titanium dioxide/carbon nanotubes (TiO 2 /CNTs) composites were prepared with the aid of ultrasonic irradiation. Products of different TiO 2 :CNTs molar ratio were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) adsorption analysis, thermogravimetric and differential thermal analysis (TGA-DSC), photoluminescence (PL) and UV-vis spectroscopy measurements (UV-vis). The photocatalytic activity was evaluated by the degradation of acetone and by the detection of the hydroxyl radical (ÁOH) signals using electron paramagnetic resonance (EPR). It is found that the crystalline TiO 2 is composed of both anatase and brookite phases. The agglomerated morphology and the particle size of TiO 2 in the composites change in the presence of CNTs. The CNTs in the composites are virtually all covered by TiO 2. Other than an increase of the surface area, the addition of CNTs does not affect the mesoporous nature of the TiO 2. Meanwhile, more hydroxyl groups are available on the surface of the composite than in the case of the pure TiO 2. The higher the content of CNTs, there is more effective in the suppression of the recombination of photo-generated e À /h + pairs. However, excessive CNTs also shield the TiO 2 from absorbing UV light. The optimal amount of TiO 2 and CNTs is in the range of 1:0.1 and 1:0.2 (feedstock molar ratio). These samples have much more highly photocatalytic activity than P25 and TiO 2 /activated carbon (AC) composite. The mechanism for the enhanced photocatalytic activity of TiO 2 by CNTs is proposed.
Photocatalytic Carbon‐Nanotube–TiO2 Composites
2009
Abstract The literature and advances in photocatalysis based on the combination of titania (TiO 2) and carbon nanotubes is presented. The semiconductor basis for photocatalysis is introduced for anatase and rutile. Furthermore, the proposed mechanisms of catalytic enhancement resulting from the pairing of the titania semiconductor with either metallic, semiconducting, or defect-rich carbon nanotubes (CNT) is discussed. Differences are apparent for the mixtures and chemically bonded CNT–TiO 2 composites.
Upgrading TiO2 Photoactivity under Visible Light by Synthesis of MWCNT/TiO2 Nanocomposite
International Journal of NanoScience and Nanotechnology, 2015
Nanocomposites of multi-walled carbon nanotubes and titanium dioxide (MWCNT/TiO2) were synthesized by the sol-gel method. Regarding hydrophobicity of carbon nanotubes (CNTs), benzyl alcohol was used as the linking agent between CNT powder and TiO2 gel which was prepared from the precursor of titanium tetraisopropoxide. The prepared samples were treated under thermal treatments. A part of the samples was heated to prepare MWCNT/TiO2 nanocomposite with anatase TiO2 and the other parts were heated until burning CNTs and prepare pseudo-tube TiO2 (PT-TiO2). The materials were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), Brunauer-Emmet-Teller (BET) measurement and UV-vis diffuse reflectance spectra (DRS). The photocatalytic activity of MWCNT/TiO2 and PT-TiO2 was studied for degradation of acetaldehyde under UV-visible and visible light irradiation. The Photocatalytic reaction was examined in a gaseous sti...
Applied Catalysis B-environmental, 2011
Combining carbon nanotubes (CNTs) with TiO 2 at the nano-scale level can promote the separation of the electron-hole charges generated upon irradiation. However, charge separation capability depends on the quality of the interfacial contact between CNTs and TiO 2 , and on the morphological and surface properties of the nanocomposites. In this study, CNT/TiO 2 nanocomposites with tailored uniform core-shell coatings were fabricated from different titania precursors (titanium ethoxide (TEOTi), titanium isopropoxide (TTIP) and titanium butoxide (TBT)) by surfactant wrapping sol-gel method. This method produces a uniform and well-defined nanometer-scale anatase titania (TiO 2 ) layer on individual CNT (multi-walled), producing a mesoporous nanocomposite film. The composites were characterized by a range of analytical techniques including TEM, XRD, BET, TGA and UV-vis to reveal the textural, crystallographic and optical properties of the composites. The nanocomposites produced from the different Ti precursors exhibited significant differences in photocatalytic activity and photocurrent within the experimental range. A thinner TiO 2 layer provides shorter distance for electron transfer to the CNT core enhancing photocatalytic activity (degradation of methylene blue). However, higher CNT content in the composites correlates with higher photocurrents. It is shown that TiO 2 film thickness is the key factor controlling electron transfer and photocatalytic activity in CNT/TiO 2 nanocomposites with a core-shell structure, when the catalyst is applied in an irradiated slurry suspension. However, it is the electronic conductivity of the nanocomposite catalyst film, which increases with CNT content that controls the rate of electron removal from the photocatalyst when it is subject to an external positive bias in an appropriate photo-electrochemical cell. Overall, the CNT/TiO 2 composite prepared from TBT performed significantly better than those prepared from TEOTi and TTIP.
TiO2 nanoparticles immobilized on carbon nanotubes for enhanced visible-light photo-induced activity
Journal of Materials Research and Technology, 2014
CNT-TiO 2 nanocomposites were prepared through (i) simple mixing of as prepared CNTs and TiO 2 nanoparticles (NPs), (ii) simple mixing of as prepared CNTs and TiO 2 NPs followed by heat treatment and (iii) simple mixing of as prepared CNTs and TiO 2 NPs followed by UV illumination. The synthesis of CNTs and TiO 2 NPs were performed individually by arc discharge in water and sol-gel methods, respectively and characterized by X-ray diffraction (XRD), ultra violet and visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The visible-light photocatalytic performance of CNT-TiO 2 nanocomposites was successfully demonstrated for the degradation of Rhodamine B (Rh. B) as a model dye at room temperature. It is found that CNT-TiO 2 nanocomposites extended the light absorption spectrum toward the visible region and considerably improved the photocatalytic efficiency under visible-light irradiation. The visible-light photocatalytic activities of CNT-TiO 2 nanocomposites in which CNTs are produced by arc discharge in deionized (DI) water at 40, 60 and 80 A arc currents and combined through three different protocols are also investigated. It was found that samples prepared at 80 A arc current and 5 s arc duration followed by UV illumination revealed best photocatalytic activity compared with the same samples prepared under simple mixing and simple mixing followed by heat treatment. The enhancement in the photocatalytic property of CNT-TiO 2 nanocomposites prepared at 80 A arc current followed by UV illumination may be ascribed to the quality of CNTs produced at this current, as was reported before.
The Journal of Physical Chemistry C, 2010
A carbon nanotubes (CNT)/TiO 2 nanocomposite photocatalyst has been prepared by a simple impregnation method, which is used, for the first time, for gas-phase degradation of benzene. It is found that the asprepared CNT/TiO 2 nanocomposite exhibits an enhanced photocatalytic activity for benzene degradation, as compared with that over commerical titania (Degussa P25). A similar phenomenon has also been found for liquid-phase degradation of methyl orange. The characterization of photocatalysts by a series of joint techniques, including X-ray diffraction, transmission electron microscopy, ultraviolet/visible (UV/vis) diffuse reflectance spectra, and photoluminescence spectra, discloses that CNT has two kinds of crucial roles in enhancement of photocatalytic activity of TiO 2. One is to act as an electron reservoir, which helps to trap electrons emitted from TiO 2 particles due to irradiation by UV light, therefore hindering electron-hole pairs recombination. The other is to act as a dispersing template or support to control the morphology of TiO 2 particles in the CNT/TiO 2 nanocomposite, and this important role was neglected in previous studies. Accordingly, a reasonable model is proposed to expain the role of CNT in CNT/TiO 2 composites as a photocatalyst for degradation of organic pollutants.
Photo-catalytic noble metallic and bimetallic nano-composites (Ag or Pd/-TiO 2 /CNT) were synthesized using a commercial source of multi-walled carbon nanotubes via a modified dry-mix metal-organic chemical vapour deposition method (MOCVD). The titania loading was varied from 10-40 wt.%, and the optimum TiO 2 /CNT photo-catalyst was determined using methylene blue degradation as a model probe reaction. Furthermore, acid-treated nanotubes and non-acid treated nanotubes were compared as a substrate for the synthesis of various titania nano-composites, and it was found that the acid treatment decreased the photo-catalytic activity of the titania CNT nano-composites. The 20 wt.% titania on CNT samples were then further modified with silver, palladium, and a combination of both metals using the MOCVD technique. It was found that the silver titania CNT nano-composites were the most effective photo-catalyst for the degradation of methylene blue. The deposition of 2% Ag on 20% TiO 2 /MWCNT resulted in 92% degradation of 50 mg/L MB in 4 h with 1 g/L of photo-catalyst. Palladium had little effect in altering the photo-catalytic activity of the titania CNT nano-composites, and the combination of both metals suppressed the photo-catalytic activity of the titania CNT nano-composites.