Room Temperature Synthesis and Thermal Evolution of Porous Nanocrystalline TiO2 Anatase (original) (raw)
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Synthesis of Anatase and Rutile TiO2 Crystals for High-Performance Dye-Sensitized Solar Cells
Advanced Materials Research, 2015
TiO 2 nanosize particles have attracted significant interest of materials scientists and physicists due to their special properties and have attained a great importance in several technological applications such as photocatalysis, sensors, solar cells and memory devices. TiO 2 nanoparticles can be produced by a variety of techniques ranging from simple chemical to mechanical to vacuum methods, including many variants of physical and chemical vapour deposition techniques. In the present research work we report the synthesis of TiO 2 nanoparticles by Sol-Gel technique. The characterization of particles was carried out by XRD and SEM techniques. The importance and applications of these nanoparticles for solar cells are also discussed in this work. Recently, the importance of tailored particles has been recognized in a number of applications such as solar cells and photonic crystals. Among the many metal oxides and their inorganic-organic hybrid materials used for the above applications, one of the most important and complex in this regard is titanium dioxide (titania). In this study, the processing parameters in an alkoxide free sol-gel synthesis of anatase titania nanoparticles were investigated. Factors affecting the sol-gel process include the reactivity of inorganic titanium salt, calcinations temperature, the influence of varying stirrer speeds on the formation of anatase particles, and the nature of hydrolytic solvent and peptisation reagent. By varying these processing parameters, materials with different microstructure and surface chemistry can be obtained.
Journal of Materials Science: Materials in Electronics, 2015
Titanium dioxide nanorods/nanoparticles (NR/ NP) were prepared via hydrothermal process. The crystallographic information of prepared samples was confirmed with PXRD, which shows anatase phase with small fraction of brookite phase. The FESEM results indicate that the formed nanostructures are having both nanorods and nanoparticles. From the HRTEM results, the lattice images of nanostructures were clearly observed, which indicates that these nanostructures possess high degrees of crystallinity. From the distance between the adjacent lattice fringes, we can assign the lattice plane on the nanostructures. The nanoparticles showed lattice spacing of 0.35 nm for the (101) plane of the anatase phase. BET analysis shows that the surface area of the sample is 37.97 m 2 /g. In the BJH approach, multiple pores are observed (2.6, 4.7 and 7.3 nm) in the structure. The obtained porous NR/NP nanostructure was applied to DSSC. The solar energy conversion efficiency (g) of the NR/NP based DSSC was about 2.12 % with J sc of 5.56 mA/cm 2 , V oc of 0.61 V and FF of 62.87 %.
MRS Proceedings, 2011
ABSTRACTDye sensitized solar cells (DSSC) are attractive because they hold promise for devices that are easy to fabricate and inexpensive. In the present work, highly crystalline mesoporous TiO2 has been synthesized by evaporation induced self assembly (EISA) method using triblock copolymer Pluronic P123 as the organic template. The synthesized TiO2 is anatase in nature with a pore size of 10-15 nm. DSSC made from mesoporous TiO2 demonstrated solar conversion efficiency of ∼7%. This comes from the benefits of increased surface roughness, surface area and uniform porosity. In addition, well ordered and crystalline pores provided good sunlight absorption and low recombination path for charge carriers. To further enhance the efficiency of the DSSCs, light scattering centers were introduced in the mesoporous TiO2 film. Nanoparticles light scatterers are introduced to scatter the incoming light and hence to increase the light harvesting capability of the device. A 26 % increase in DSSC e...
Advances in porous and high-energy (001)-faceted anatase TiO 2 nanostructures
In this review, we present a summary of research to date on the anatase polymorph of TiO 2 nano-structures containing high-energy facet, particularly (001) plane, with porous structure, covering their synthesis and their application in photocatalysis as well as a review of any attempts to modify their electrical, optical and photocatalytic properties via doping. After giving a brief introduction on the role of crystalline facet on the physico-chemical properties of the anatase TiO 2 , we discuss the electrical and optical properties of pristine anatase TiO 2 and after being doped with both metal and non-metals dopants. We then continue to the discussion of the electrical properties of (001) faceted anatase TiO 2 and their modification upon being prepared in the form of porous morphology. Before coming to the review of the photocatalytic properties of the (001) faceted anatase and (001) with porous morphology in selected photocatalysis application, such as photodegradation of organic pollutant, hydrogenation reaction, water splitting, etc., we discuss the synthetic strategy for the preparation of them. We then end our discussion by giving an outlook on future strategy for development of research related to high-energy faceted and porous anatase TiO 2 .
Nanocrystalline Titanium Oxide Electrodes for Photovoltaic Applications
Journal of the American Ceramic Society, 2005
During the past five years, we have developed in our laboratory a new type of solar cell that is based on a photoelectrochemical process. The light absorption is performed by a monolayer of dye (i.e., a Ruthenium complex) that is adsorbed chemically at the surface of a semiconductor (i.e., titanium oxide (TiO 2 )). When excited by a photon, the dye has the ability to transfer an electron to the semiconductor. The electric field that is inside the material allows extraction of the electron, and the positive charge is transferred from the dye to a redox mediator that is present in solution. A respectable photovoltaic efficiency (i.e., 10%) is obtained by the use of mesoporous, nanostructured films of anatase particles. We will show how the TiO 2 electrode microstructure influences the photovoltaic response of the cell. More specifically, we will focus on how processing parameters such as precursor chemistry, temperature for hydrothermal growth, binder addition, and sintering conditions influence the film porosity, pore-size distribution, light scattering, and electron percolation and consequently affect the solar-cell efficiency.
Progress in Photovoltaics: Research and Applications, 2014
Multistep hydrothermal (MSH) process is employed for growth of TiO 2 nanocorals onto the conducting fluorine-doped tin oxide-coated glass substrates. The surface morphological features and physical properties of TiO 2 films were investigated by field emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Fourier transform Raman spectroscopy, room temperature photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The surface morphology revealed the formation of TiO 2 corals having nanosized (30-40 nm) polyps. The photoelectrochemical properties of the TiO 2 nanocoral electrodes were investigated in 0.1 M NaOH electrolyte under ultraviolet illumination. The results presented in this study highlight two major findings: (i) tuning the photoelectrochemical response and photoconversion efficiency via controlled thickness of TiO 2 nanocorals by MSH route and (ii) the substantial increase in short-circuit photocurrent (J sc ) because of the improved charge transport through TiO 2 nanocorals prepared via MSH process.
Structural, electronic, and surface properties of anatase TiO2 nanocrystals from first principles
Physical Review B, 2008
The structural and electronic properties of anatase TiO 2 nanocrystals ͑NCs͒ are investigated through firstprinciples calculations. The dependence of the structural properties ͑e.g., NC volume variations͒ on the surface chemistry is discussed by considering two different surface coverages ͑dissociated water and hydrogens͒. Both prevent a pronounced reconstruction of the surface, thus ensuring a better crystalline organization of the atoms with respect to the bare NC. In particular, the results for the hydrated NC do show the largest overlap with the experimental findings. The band-gap blueshift with respect to the bulk shows up for both the bare and the hydrated NC, whereas hydrogen coverage or oxygen desorption from the bare NCs induce occupied electronic states below the conduction levels thus hindering the gap opening due to quantum confinement. These states are spatially localized in a restricted region and can be progressively annihilated by oxygen adsorption on undercoordinated surface titanium atoms. Formation energy calculations reveal that surface hydration leads to the most stable NC, in agreement with the experimental finding that the truncated bipyramidal morphology is typical of the moderate acidic environment. Oxygen desorption from the bare NC is unfavorable, thus highlighting the stabilizing role of surface oxygen stoichiometry for TiO 2 . Available experimental data on the electronic and structural properties of TiO 2 NCs are summarized and compared with our results.
International Journal of Hydrogen Energy, 1999
Unlike the rutile^the anatase phase of TiO 1 has not been extensively employed for fabrication of PEC cells primarily due to the di.culty in the synthesis of a stable anatase structural variant[ The present investigation is focused on the synthesis of the anatase phase and its use as a photoelectrode of high e.ciency PEC Solar Cells[ TiO 1 \ in the nano! structured form\ has been prepared by the hydrolysis of Titanium "IV# isopropoxide solution[ The nanostructured TiO 1 "anatase# stable phase has been synthesised by sintering the synthesised _lm at ½499>C with a heating rate of 0>C:min for a duration of 2 h in argon[ The _lms of nanostructured TiO 1 anatase phase have been used as photoelectrodes in PEC solar cells[ An improvement in TiO 1 "ns# anatase phase photoelectrode carried out in the present work corresponds to admixing In 1 O 2 to improve the spectral response[ It has been found that admixing In 1 O 2 with TiO 1 "ns# anatase phase improves the solar spectral response[ The structural\ microstructural\ optical\ and photoelectrochemical properties of the TiO 1 "ns# anatase phase and TiO 1 "ns# anatase!In 1 O 2 photoelectrode have been studied[ The response of TiO 1 "ns# anatase phase bearing photoelectrode based PEC solar cell corresponds to V OC ¼ 359 mV\ I SC ¼ 1[3 mA:cm 1 and for its In 1 O 2 doped version\ these are V OC ¼ 539 mV and I SC ¼ 09[3 mA:cm 1 [
Advances in OptoElectronics, 2011
High surface area titania with crystalline anatase walls has been synthesized using ordered large mesoporous carbon as a template. The pore structure of mesoporous carbon is infiltrated with titanium tetraisopropoxide solution at room temperature and the mixture is subjected to heat treatment at in presence of air to complete removal of the template. The prepared crystalline anatase frameworks are characterized by XRD, N2adsorption and HR-TEM. The nitrogen adsorption-desorption analysis of the prepared anatase titania particles exhibits BET specific surface area of 28 m2/g. The dye-sensitized solar cells performance of this anatase titania material has been tested and energy conversion efficiency of 3.0% is achieved under AM 1.5 sunlight. This work reports a new approach for fabrication of nanocrystalline anatase titania by simple hard templating technique for the first time and their applications for dye-sensitized solar cell.