Morphology control of CNT-TiO2 hybrid materials and rutile nanotubes (original) (raw)
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Carbon–Inorganic Hybrid Materials: The Carbon-Nanotube/TiO2 Interface
Advanced Materials, 2008
Carbon-inorganic hybrid materials are a new class of functional materials that gained tremendous interest in recent years owing to their exceptional optical, mechanical, electrical, and thermal properties, thus enabling the use in photochemical, catalytic, and electrochemical technologies. [1] Titanium dioxide (TiO 2) is one of the most important transition metal oxides. Its remarkable chemical and physical properties [2] commend it to applications such as gas sensing, [3] photo-chromic devices, [4] photocatalysis (e.g., water and air purification, self cleaning surfaces), [5,6] and ''dye-sensitized TiO 2 solar cells''. [7,8] Generally, for TiO 2 , a large specific surface area is crucial to achieve high (photo)-catalytic activities as well as a good dispersion of adsorbed metals and metal-organic compounds. Thus, the fabrication of TiO 2 with nanometer-scale morphology is of considerable interest. While chemical vapor deposition (CVD) and flame synthesis are possible routes, [9] the sol-gel process provides particularly good control from the molecular precursor to the final product, as well as giving high purity and homogeneity. [10,11] In recent years, there has been considerable progress in the production of novel functional materials by coupling TiO 2 with other inorganic/organic materials. [12,13] For instance, Kamat et al. reported that combining single-walled carbon nanotubes (SWCNTs) with TiO 2 in a photovoltaic device enhanced the photoconversion efficiency from 7 to 15%. [14] A further increase would crucially depend on the improvement of the CNT/TiO 2 interface. CNTs have also been used to improve the mechanical performance of thin-film TiO 2. [15,16] Other workers have dispersed CNTs in a TiO 2 sol [17] and studied the immobilization of TiO 2 on CNTs, [18,19] while CNTs can be applied to the synthesis of various inorganic nanotubes. [13,20,21] Recently, we showed that CNTs could support the anatase coating during its phase transformation into rutile, leading to the first synthesis of rutile nanotubes. [22] CNTs straight from CVD synthesis (pristine CNTs) are hydrophobic and thus need to be functionalized with hydrophilic organic groups to provide attractive interaction with the titanium sol. [13,17] Such groups are typically attached
Synthesis and characterization of carbon nanotubes–TiO 2 nanocomposites
Carbon, 2004
The main objective of this paper is to coat carbon multiwall nanotubes surface with TiO 2 as anatase in view of photocatalytic application for these nanocomposites. Carbon nanotubes were produced by catalytic decomposition of acetylene at 600°C. The coating was performed by a sol-gel method using classical alkoxides as Ti(OEt) 4 and Ti(OPr i ) 4 and by hydrothermal hydrolysis of TiOSO 4 , leading to different TiO 2 morphologies. In using the sol-gel method, nanotubes are coated either with a continuous TiO 2 thin film when the precursor is Ti(OEt) 4 , or with TiO 2 nanoparticles when the precursor is Ti(OPr i ) 4 . By hydrothermal treament, more compact and crystalline nanocomposites are obtained.
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.
Anatase-type TiO 2 nanotube arrays (TiO 2-NTAs) were grown on Ti foil by anodic oxidation in CH 3 COOH/NH 4 F solutions followed by thermal treatment. The surface of TiO 2-NTAs was further decorated by palladium and silver metal clusters through a chemical-reduction method and its photocatalytic activity was tested by investigating the degradation of p-nitrophenol (PNP) in aqueous solution under visible-light irradiation and electrical polarization. The effects of preparation variables both on microstructural properties of samples and photocatalytic activity were examined by using the 3D response surface and the 2D contour plots. The experimental investigations carried out by using XRD, SEM, HRTEM, EDS, XRF, ICP-AES, XPS, DRS, and PL, demonstrated a strong relation between the phase structure and the photocatalytic activity of TiO 2-NTAs. Titania nanotubes grown in acetic acid solution and thermally post-treated have stable anatase crystal structure, to a point that by performing annealing at 800 • C for 3 h, only the 35% of anatase transforms into rutile. Finally, it was shown that the TiO 2-NTAs decorated with Pd(0.72 wt%) and Ag(1.26 wt%) particles show higher photocatalytic activity compared with nanotubes modified with single metal particles. It is believed that the high photoactivity of TiO 2 nanotubes decorated with Pd–Ag heterostructures is due to the prolonged lifetimes of photogenerated electron–hole pairs. The possible mechanism for the enhanced photocatalytic activity is discussed in detail.
Journal of colloid and interface …, 2011
A hybrid assembly composed of thin multi-walled carbon nanotubes (t-MWCNT) and titanium dioxide (TiO 2 ) has been prepared by using ''click'' chemistry for photocatalytic applications. TiO 2 -decorated t-MWCNT hybrids with anatase phase TiO 2 were obtained from the reaction of an azide moiety-containing TiO 2 with alkyne-functionalized t-MWCNTs. The hybrids were systematically characterized using Fourier transform infrared spectroscopic (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDX), and X-ray diffraction (XRD) measurements. The nanohybrid has been proved to be highly active and robust for photocatalytic degradation of methyl orange. The click coupling approach is a simple and convenient route to efficiently assemble TiO 2 on the surface of carbon nanotubes, and can be extended to obtain many other nanoparticle hybrids based on carbon nanotubes.
Synthesis of a CNT-grafted TiO2 nanocatalyst and its activity triggered by a DC voltage
Nanotechnology, 2007
Carbon nanotube (CNT)-grafted TiO 2 (CNT/TiO 2 ) was synthesized as an electrically conductive catalyst that exhibits redox ability under electrical excitation besides ultraviolet (UV) irradiation. The CNT/TiO 2 material was synthesized by a two-step process. Ni nanoparticles were photodeposited onto TiO 2 first. The Ni nanoparticles then served as seeds for the growth of CNTs using the chemical vapor deposition (CVD) of C 2 H 2 . The CNT/TiO 2 nanocomposite exhibits strong oxidation activity toward NO gas molecules via both photocatalysis under UV irradiation and electrocatalysis under a DC voltage of 500 V in dark conditions.
Hydrothermal synthesis of single-walled carbon nanotube–TiO2 hybrid and its photocatalytic activity
Applied Surface Science, 2013
A single-walled carbon nanotube (SWCNT)-TiO 2 hybrid was prepared hydrothermally by direct growth of TiO 2 nanoparticles on the surface of functionalized SWCNTs to develop highly efficient photocatalysts. The SWCNT-TiO 2 hybrid was characterized by X-ray diffraction, electron microscopy, N 2-adsorption analysis, FT-IR, Raman, and UV-vis spectroscopy. The photocatalytic activity of the SWCNT-TiO 2 hybrid was examined by the photocatalytic degradation of pirimicarb. Although the SWCNT-TiO 2 hybrid exhibits no visible-light-induced activity, the photocatalytic degradation efficiency of pirimicarb over TiO 2 can be increased significantly with the introduction of SWCNTs (2-3 times) because SWCNTs can act as electron conductors that hinder the recombination of photo-generated electrons and holes. Compared with a multi-walled carbon nanotube-TiO 2 hybrid, it can be found that the electronic configurations of carbon nanotubes significantly affect the photocatalytic activity of carbon nanotube-TiO 2 hybrid. Metal-typed SWCNTs act more as an electrical conductor than a photosensitizer, which efficiently suppress charge recombination, improve interfacial charge transfer, and improve the photoactivity.