Carbon nanotube/titanium dioxide (CNT/TiO 2) core–shell nanocomposites with tailored shell thickness, CNT content and photocatalytic/photoelectrocatalytic properties (original) (raw)
2011, Applied Catalysis B-environmental
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.
Related papers
2015
ABSTRAK ii ACKNOWLEDGEMENTS iii APPROVAL iv DECLARATION vi LIST OF TABLES x LIST OF FIGURES xi LIST OF SYMBOLS xiii LIST OF ABBREVIATIONS xiv CHAPTER 1 NANOMATERIAL AND NANOTECHNOLOGY 1.1 Introduction 1.2 Problem Statement 1.3 Research Objectives 1.4 Scope of the research 1.5 Significance of the research 1.6 Thesis outline 2 LITERATURE REVIEW 2.1 Introduction 2.2 Titanium dioxide (TiO2) 2.3 Carbon nanotube 2.4 Deposition of TiO2 on CNTs surface 2.5 Characterization of CNTs/TiO2 nanocomposite 2.6 Photocatalytic activity of CNT/TiO2 nanocomposites 2.6.1 Light intensity 2.6.2 pH of the solution 2.6.3 Reaction temperature 2.6.4 Photocatalyst concentration 2.6.5 Concentration of the pollutant 3 THEORY 3.1
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.
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
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.
Stabilized mesoporous TiO2 was synthesized by evaporation induced self assembly (EISA) method and mechanically incorporated into single-walled carbon nanotubes (SWCNT) with different ratios. The physicochemical properties of the nanocomposites (mesoporous TiO2/SWCNT) materials were investigated by BrunauereEmmetteTeller (BET) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), photoluminescence (PL) and ultravioletevisible (UV eVis) spectroscopy measurements. The catalytic activity of mesoporous TiO2 and nanocomposites were assessed by examining the degradation of rhodamine B as model aqueous solution under visible light. CNTs are facilitating the photocatalytic activity of mesoporous TiO2 in the degradation of rhodamine B efficiently
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...
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.