Surface engineering of TiO2-MWCNT nanocomposites towards tuning of functionalities and minimizing toxicity (original) (raw)
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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
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.
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.
Fabrication of carbon-modified TiO2 nanotube arrays and their photocatalytic activity
Materials Letters, 2008
TiO 2 nanotube (TN) arrays were fabricated by an anodic oxidation process. Through a heat treatment of the as-fabricated TN arrays under a continuous Ar and acetylene flux, carbon-modified TN (C-TN) arrays were obtained. The as-fabricated catalysts were characterized by FE-SEM, HRTEM, XPS, Raman and UV-Vis spectra. Moreover, photocatalytic activity of the C-TN arrays was evaluated through the photodegradation of aqueous methyl blue. The experiments demonstrated that the C-TN arrays display an excellent photocatalytic activity. Under sunlight irradiation, the C-TN arrays are able to almost completely decompose the methylene blue pollutant of 1 × 10 − 5 M within 300 min.
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.
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
Photocatalytic noble metallic and bimetallic nanocomposites (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 nanocomposites. 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 nanocomposites 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 photocatalytic activity of the titania CNT nanocomposites, and the combination of both metals supressed the photo-catalytic activity of the titania CNT nanocomposites.