Synthesis and Characterization of Anatase–TiO2 Thin Films
T1 - Synthesis and characterization of TiO2 thin films on organic self-assembled monolayers
Synthesis and characterization of brookite/anatase complex thin ..
The advantages in using nanoscale materials for electrochemical energy storage are generally attributed to short diffusion path lengths for both electronic and lithium ion transport. Here, we consider another contribution, namely the charge storage from faradaic processes occurring at the surface, referred to as pseudocapacitive effect. This paper describes the synthesis and pseudocapacitive characteristics of block copolymer templated anatase TiO2 thin films synthesized using either sol−gel reagents or preformed nanocrystals as building blocks. Both materials are highly crystalline and have large surface areas; however, the structure of the porosity is not identical. The different titania systems are characterized by a combination of small- and wide-angle X-ray diffraction/scattering, combined with SEM imaging and physisorption measurements. Following our previously reported approach, we are able to use the voltammetric sweep rate dependence to determine quantitatively the capacitive contribution to the current response. Considerable enhancement of the electrochemical properties results when the films are both made from nanocrystals and mesoporous. Such materials show high levels of capacitive charge storage and high insertion capacities. By contrast, when mesoscale porosity is created in a material with dense walls (rather than porous walls derived from the aggregation of nanocrystals), insertion capacities comparable to templated nanocrystal films can be achieved, but the capacitance is much lower. The results presented here illustrate the importance of pseudocapacitive behavior that develops in high surface area mesoporous oxide films. Such systems provide a new class of pseudocapacitive materials, which offer increased charge storage without compromising charge storage kinetics.
TiO2 is widely used in applications like photocatalysis, sensors, solar cells, and memory devices because it is inexpensive, abundant, nontoxic and stable in aqueous solution. Another exciting application where TiO 2 has the potential to be a very useful catalyst is the clean hydrogen generation using solar radiation. Energy consumption is increasing every year and, as a result, renewable and sustainable alternative energy sources are becoming increasingly important. Therefore, clean hydrogen generation research is becoming more and more important. This study aims at the preparation and characterization of nitrogen and carbon (N-C) codoped TiO 2 photoanode material that could potentially be used in photoelectrochemical cells for hydrogen generation. The solar spectrum peaks around 500 nm (2.48 eV) which is in the visible part of the spectrum. The photoanode material to be used for solar hydrogen generation should absorb visible light photons to yield high efficiency. The challenge with TiO2 is that the wide band gap (3.00-3.20 eV) absorbs only ultra-violet (UV) photons and only a small percentage of the solar spectrum is in the UV range. There are various ways to overcome the challenge of sensitizing the material to visible light absorption and this study focuses on one of the most promising ways: band modification of TiO 2 by N-C codoping. The role of pure oxygen pressure on pulsed laser deposited N-C codoped TiO2 films were investigated. At low pressures rutile phase of TiO2 was dominant and a microstructure with densely packed grains was obtained. However, at high pressures anatase phase became dominant and columnar structure was favored. Therefore, the anatase-rutile phase ratio as well as the microstructure of the films can be controlled by adjusting oxygen pressure and introducing N and C into the TiO 2 matrix. Optimized oxygen pressure and higher doping concentrations yielded films with more effective absorption in the visible region. The preparation and characterization of pulsed laser deposited N-C codoped TiO2 thin films were investigated for dopant incorporation using N2 and CH4 gases. Polycrystalline anatase structured films were obtained. A 2 theta shift of the anatase (101) X-ray diffraction main peak towards lower values indicated carbon incorporation into the lattice. N incorporation was confirmed with observed Ti-N bonds using X-ray photoelectron spectroscopy. Optical data showed significant reduction, approximately 1.00 eV, of the band gap. The reduction of the band gap allowed the photons in the visible part of the solar spectrum to be absorbed. Through a collaborative work with scientists at Brookhaven National Laboratory and Yonsei University, precise modeling of the electronic structure of N-C codoped TiO2 films were carried out to reveal the underlying physics of band gap reduction. Experimental results were compared with first-principle density functional theory calculations. Hard X-ray photoelectron spectroscopy showed that O, N and C 2p states overlapped effectively and shifts in the valence band maximum towards the Fermi level were observed. Optical band gap results showed that N-C codoping is an effective route for band gap reduction in TiO 2 . Comparison of the measured valence band structure with theoretical photoemission density of states further revealed C substitution on the Ti site and N substitution on the O site. Finally, films grown using radio frequency (rf) magnetron sputtering were compared with the pulsed laser deposited films. Sputtered N-C codoped TiO2 films showed phase transformation from anatase to rutile at constant argon pressure with increasing doping concentration. Moreover, with slow-rate N-C codoping of TiO2 , a texturing effect was observed in X-ray diffraction scans such that anatase (004) Bragg reflection plane became more favored over anatase (101). Optical band gap was reduced but the reduction was not as significant as in the films prepared with the pulsed laser deposition method. Electrochemical methods were applied in the photoelectrochemical cell and the sample prepared by using TiO 2 target with 8% N and C atomic concentrations found to have slightly better photoactivity relative to the other N-C codoped samples. However, due to preferential anatase (004) plane, overall efficiency of N-C codoped films was low. In conclusion, pulsed laser deposition is preferred over rf magnetron deposition for the purpose of band gap reduction of TiO2 by N and C codoping. Pulsed laser deposited films showed continuum in C and N 2 p dopant states within the forbidden region and these states overlapped well with O 2p states. For this reason, optical band gap measurements showed significant reduction. Therefore, pulsed laser deposition of N-C codoped TiO2 films is a possible way of photoanode fabrication for solar hydrogen generation. (Abstract shortened by UMI.)
Synthesis of TiO2 thin films by the SILAR method and …
N2 - Self-assembled monolayers (SAMs) bearing sulfonate (-SO3H) surface functional groups, on single-crystal Si wafers, were used as substrates for the deposition of TiO2 thin films from aqueous solutions. Polycrystalline TiO2 thin films over 50 nm thick formed in 2 h by hydrolysis of TiCl4 in aqueous HCl solutions at 80 °C. The films were pore-free, showed excellent adherence and uniformity, and consisted of anatase crystallites 2-4 nm in diameter. Annealing at temperatures up to 600 °C caused coarsening of the anatase grains, but no loss of adherence or structural integrity.
Ghrairi , Bouaicha , Structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique, , Year: 2012, Volume: 7, Page: 357 DOI:
Synthesis, characterization and optical ..
Shin, H., Collins, R.J., De Guire, M.R., Heuer, A.H. and Sukenik, C.N.: Synthesis and Characterization of TiO2 Thin Films on Organic Self-Assembled Monolayers: II. Film Formation via an Organometallic Route. J. Mater. Res. 10  699-703 (1995)
AB - TiO2 films were prepared on a silicon or soda-glass substrate using a sol suspension. The TiO2 film on the silicon substrate was composed of pure anatase phase and showed almost no contaminations. In contrast, the TiO2 film on the soda-glass substrate was composed of anatase and brookite phases. The diffusion of Na into the TiO2 film on the soda-glass substrate was observed by XPS, and Na was concentrated on the surface of the film. The yield of the brookite phase increased with decreasing distance from the surface of the film on the soda-glass substrate. Na promoted the formation of the brookite phase, although the preparative procedure was used for anatase synthesis.
Synthesis and characterization of brookite/anatase …
although the preparative procedure was used for anatase synthesis
A new and effective method for the preparation of nanocrystalline TiO 2 (anatase) thin films is presented
Preparation and Characterization of ..
02/05/2015 · Synthesis, characterization and photocatalytic behavior of Ag ..
Synthesis, Characterization and Photocatalytic Properties of ..
01/09/2000 · Preparation and Characterization of Nanostructured TiO2 Thin ..
characterization and photocatalytic properties of ..
AB - Synthesis of titania (TiO2) nanorods on various substrates has recently attracted attention for energy and environmental applications. Herein, we report growth of nanostructured TiO2 on Si(111) and glass borosilicate substrates by a two-step method. A thin film of anatase TiO 2 was first laid down by spin coating and annealing, followed by the growth of rutile TiO2 nanorods with a hydrothermal method. To understand the role of the polycrystalline anatase TiO2 seed layer, we selected a relatively high temperature for the hydrothermal reaction, e.g., 175 °C at which no rutile TiO2 nanorods could grow without the precoated anatase TiO2 layer. The morphology and microstructure of both the polycrystalline anatase and rutile nanorod layers were characterized by electronmicroscopy and x-ray powder diffraction. Such a two-step fabrication method makes it possible to grow TiO2 nanorods on almost any substrate.
Anatase and rutile TiO2 thin films prepared ..
N2 - Synthesis of titania (TiO2) nanorods on various substrates has recently attracted attention for energy and environmental applications. Herein, we report growth of nanostructured TiO2 on Si(111) and glass borosilicate substrates by a two-step method. A thin film of anatase TiO 2 was first laid down by spin coating and annealing, followed by the growth of rutile TiO2 nanorods with a hydrothermal method. To understand the role of the polycrystalline anatase TiO2 seed layer, we selected a relatively high temperature for the hydrothermal reaction, e.g., 175 °C at which no rutile TiO2 nanorods could grow without the precoated anatase TiO2 layer. The morphology and microstructure of both the polycrystalline anatase and rutile nanorod layers were characterized by electronmicroscopy and x-ray powder diffraction. Such a two-step fabrication method makes it possible to grow TiO2 nanorods on almost any substrate.
for anatase thin films grown ..
The synthesis of Fe-doped TiO2 thin film using spin coating method was studied. Effects of aging time on the deposited thin film were investigated. Titanium butoxide (C16H36O4Ti) as a precursor solution was mixed with the FeCl3. Spin coating process was carried out on three types of precursor solution: (1) spin-coating process performed immediately after the precursor solution was made, (2) spin-coating process performed after solution was aged for 24 hours, (3) aged for 24 and (4) spin-coating after aging the precursor for 72 hours. Heating was carried out on the resulting thin film at temperature of 400∘C. The morphology of TiO2 layers was characterized using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Elemental and phase composition of the films was determinedusing EDX and X-ray diffraction (XRD). We found that the best TiO2layer is obtained when spin-coating process is done after aging the precursor for 72 hours. The layer shows a more uniform particle distribution on the substrate and a more monodisperse particle size dominated by the anatase phase.
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