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Influence of Amorphous TiO2-x on Titania Nanoparticle Growth and Anatase-to-Rutile Transformation
2012
Amorphous TiO2-x formed together with precursors and anatase nuclei, during TiCl4 hydrolysis at soft conditions, influences both crystal growth and phase stability. The highly defective nanoparticles of anatase grow by reaction of their basic hydroxyls with acidic ones of TiO2 precursor species. The growth of anatase crystals, however, is affected by their interactions with simultaneously formed amorphous TiO2-x which increasingly covers the particles hindering the anatase-precursor contact. The interactions among anatase and amorphous and precursor components have been studied by H-1-MAS (magic angle spinning) NMR spectroscopy. The interaction between acid and basic hydroxyls favors the fo…
Preparation characterization and photocatalytic activity of polycrystalline ZnO/TiO2 systems. 2. Surface, bulk characterization, and 4-nitrophenol ph…
2001
Electron spin resonance spectroscopy (ESR), Fourier transform infrared spectroscopy (FTIR), and monitoring of pyridine (py) and boric acid trimethyl ester (BATE) adsorption for determining surface acidity and basicity, respectively, were used to carry out further characterization of mixed ZnO/TiO2 polycrystalline solids prepared by different methods. Moreover, the powders were tested in a batch photoreactor for a probe reaction, i.e., 4-nitrophenol photodegradation in aqueous medium. ESR results indicated the presence of signals attributable to Zn+ species in ZnO/TiO2 (anatase) solids, while in ZnO/TiO2 (rutile) samples the presence of zinc induced only the formation of signals probably due…
Step-by-Step Growth of HKUST-1 on Functionalized TiO2 Surface: An Efficient Material for CO2 Capture and Solar Photoreduction
2018
The present study reports on a simple preparation strategy of a hybrid catalyst, TiO2/HKUST-1, containing TiO2 anatase nanoparticles (NPs) with tailored morphology and photocatalytic activity coupled with a porous metal-organic framework (MOF), namely HKUST-1, as an advanced material for the CO2 photocatalytic reduction. In detail, TiO2/HKUST-1 catalyst was prepared via an easy slow-diffusion method combined with a step-by-step self-assembly at room temperature. The growth of crystalline HKUST-1 onto titania surface was achieved by functionalizing TiO2 nanocrystals, with phosphoesanoic acid (PHA), namely TiO2-PHA, which provides an intimate contact between MOF and TiO2. The presence of a cr…
Preparation characterization and photocatalytic activity of polycrystalline ZnO/TiO2 systems. 1. Surface and bulk characterization
2001
Polycrystalline ZnO/TiO2 solids have been prepared with four different methods using home prepared TiO2 (anatase) or TiO2 (rutile) as supports and Zn(NO3)2·6H2O or Zn(CH3COO)2·2H2O as precursors for ZnO. The bulk and surface properties of the samples were investigated by means of TG-DTA, XRD, TEM, SEM-EDAX, XPS, BET surface area determination, and porosity measurements. XRD and TEM results indicate that no significant defect structures exist in any of the samples. The ZnO crystallinity and its enrichment on the surface of TiO2 particles were dependent on the preparation method. The surface areas generally decrease by increasing the amount of ZnO except when ZnO from Zn(CH3COO)2·2H2O was sup…
Effect of the addition of different doping agents on visible light activity of porous TiO2 photocatalysts
2018
Abstract The influence of the addition of different doping agents (N, W and Hf) on the macroporous TiO2 photoactivity toward the Rhodamine B degradation and ethanol photo-oxidation was evaluated. The samples were characterized by XRD, XPS, SEM, TEM, N2 adsorption-desorption, UV–vis Diffuse Reflectance and Photoluminescence spectroscopies to study also the changes in the physico-chemical properties due to the presence of dopants. The photonic effect and the high ordered porous structure of the macroporous TiO2 that lead to increase the path length of the light, were the key factors that allow to enhance the catalytic activity towards the dye and VOC degradation under visible and solar light …
Stabilizing nanostructured lithium insertion materials via organic hybridization: A step forward towards high-power batteries
2014
Abstract Herein, we present the electrochemical characterization of carbon-coated TiO 2 nanorods, obtained by carbonizing RAFT (reversible addition fragmentation chain transfer) polymerization derived block copolymers anchored on anatase TiO 2 nanorods. These carbon-coated TiO 2 nanorods show an improved electrochemical performance in terms of first cycle reversibility, specific capacity, cycling stability, and high rate capability. More importantly, however, the structural disordering observed in the uncoated TiO 2 nanorods by means of galvanostatic and potentiodynamic cycling as well as ex situ XRD analysis, does not occur for the carbon-coated material. Preventing this structural disorde…
Removal of Surface Oxygen Vacancies Increases Conductance Through TiO(2) Thin Films for Perovskite Solar Cells
2019
[Image: see text] We report that UV–ozone treatment of TiO(2) anatase thin films is an efficient method to increase the conductance through the film by more than 2 orders of magnitude. The increase in conductance is quantified via conductive scanning force microscopy on freshly annealed and UV–ozone-treated TiO(2) anatase thin films on fluorine-doped tin oxide substrates. The increased conductance of TiO(2) anatase thin films results in a 2% increase of the average power conversion efficiency (PCE) of methylammonium lead iodide-based perovskite solar cells. PCE values up to 19.5% for mesoporous solar cells are realized. The additional UV–ozone treatment results in a reduced number of oxygen…
Tailoring the Structural, Optical, and Photoluminescence Properties of Porous Silicon/TiO2 Nanostructures
2015
The structural, optical, and photoluminescence properties of porous silicon (PSi)/titanium dioxide (TiO2) nanostructures were investigated. PSi structures consisting of macro- and mesoporous layers were fabricated by metal-assisted chemical etching, and then TiO2 was introduced inside the PSi matrix using the atomic layer deposition technique. We performed scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectroscopy, ellipsometry, and photoluminescence (PL) spectroscopy to characterize the prepared and annealed PSi/TiO2 nanostructures. TEM and Raman analyses revealed that TiO2 had a crystalline anatase stru…
Rate of photon absorption and turnover number: two parameters for the comparison of heterogeneous photocatalytic systems in a quantitative way
1993
Abstract In order to correctly compare the performance of different photocatalytic systems using polycrystalline semiconductor oxides, two parameters are proposed: the rate of photon absorption (rpa) and the turnover number (tn). From these quantities the quantum yield (qy), which indicates the efficiency of the absorbed photons for promoting a reaction event, can be determined. The phenol photodegradation reaction, carried out in aqueous dispersions of polycrystalline TiO2 (anatase) of different preparation methods and sources, has been used as “test reaction” in order to determine the tn, rpa and qy values.
Home-prepared anatase, rutile, and brookite TiO2 for selective photocatalytic oxidation of 4-methoxybenzyl alcohol in water: reactivity and ATR-FTIR …
2009
5th European Meeting on Solar Chemistry and Photocatalysis -- OCT 04-08, 2008 -- Palermo, ITALY