Search results for "Photocatalysis."
showing 10 items of 584 documents
Temperature dependent photoluminescence of photocatalytically active titania nanopowders
2007
Abstract Temperature photoluminescence (PL) in the sub-ambient range has been developed as a tool for characterizing photocatalytic materials. The use of well-characterized TiO2 nanoparticles with calibrated particle sizes allowed to face the temperature dependent PL results with the photocatalytic activity and several important physico-chemical parameters. In the relaxation of the photoexcited electron/hole pairs, the transfer towards surface sites is in competition with radiative and non-radiative recombinations. Temperature dependent PL appears thus to be a very sensitive technique to study the efficiency of the electron or the hole trapping at the surface of titania nanoparticles where …
Visible-light-accelerated amination of quinoxalin-2-ones and benzo[1,4]oxazin-2-ones with dialkyl azodicarboxylates under metal and photocatalyst-fre…
2021
A direct sp3 C-H amination of cyclic amines (dihydroquinoxalinones and dihydrobenzoxazinones) with dialkyl azo dicarboxylates accelerated by visible-light irradiation under metal and photocatalyst-free conditions is described. This protocol features very mild reaction conditions for the synthesis of aminal quinoxaline and benzoxazine derivatives with good to high yields (up to 99%). These aminal derivatives respresent versatile building blocks for the divergent synthesis of quinoxalin-2-one derivatives.
Analytical control of photocatalytic treatments: degradation of a sulfonated azo dye
2003
The degradation of Methyl Orange (C(14)H(14)N(3)SO(3)Na), chosen as a model sulfonated azo dye, was investigated in aqueous solutions containing suspended polycrystalline TiO(2) particles under irradiation with simulated sunlight. The dye disappearance and the formation of the mineralization end products were monitored; the formation of the main transient intermediates was also examined in detail. Particular attention was devoted to the identification and to the evolution of fragments retaining the chromophoric group. The comparison of data coming from various analytical techniques led to a possible reaction mechanism for the degradation process, giving insight into an aspect of the treatme…
Visible-light-induced oxidation of trans-ferulic acid by TiO2 photocatalysis
2012
Abstract The oxidation of trans-ferulic acid (C10H10O4) in aqueous TiO2 dispersion occurs via the formation of a charge-transfer complex on the TiO2 surface that is able to absorb visible light (λ ⩾ 400 nm). The main product is CO2, whereas secondary oxidation products are organic species such as vanillin, caffeic acid, homovanillic acid, and vanillylmandelic acid. Oxidation through the formation of a charge-transfer complex occurs only in the presence of specific TiO2 samples. Experiments in the absence of oxygen, in the presence of bromate ions and by using a phosphate-modified TiO2, have been carried out for investigating the reaction mechanism. In order to study the interaction between …
Fundamentals of photocatalysis: The role of the photocatalysts in heterogeneous photo-assisted reactions
2021
Abstract This chapter provides some general definitions of heterogeneous photocatalysis and evaluates its performance, which is influenced by the parameters most closely related to the properties of the solid material that acts as a photocatalyst. It also discusses aspects of heterogeneous photocatalytic reactions and explains the properties that influence photoactivity. Finally, the chapter examines thermodynamic and kinetic features, including mechanistic details and parameters to define the reaction rate and correlates them to the effects of the interaction of light with the photocatalyst surface and adsorption-desorption of species involved in heterogeneous photo-assisted reactions.
Photocatalytic CO2 Reduction in Gas-Solid Regime in the Presence of Bare, SiO2 Supported or Cu-Loaded TiO2 Samples
2013
Both commercial and home prepared (HP) TiO2 samples have been tested for the photocatalytic reduction of CO2. (HP) TiO2 powders were prepared by using TiCl4 or Ti(OC4H9)4 as the precursors to obtain HP1 and HP2 samples, respectively. Also HP Cu-loaded and SiO2 supported TiO2 powders were prepared. The HP samples were more active than the commercial ones for the photoreduction of CO2 with and without water vapour. HP1 produced mainly formaldehyde, HP2 principally methane. Acetaldehyde was found to be the primary product obtained when HP1 was supported on SiO2. The addition of Cu increased the photocatalytic reactivity either of bulk and SiO2-supported HP1. In particular, 1 wt % of Cu improve…
Highly textured boron/nitrogen co-doped TiO2 with honeycomb structure showing enhanced visible-light photoelectrocatalytic activity
2020
International audience; In this work, we report a novel photocatalyst based on boron and nitrogen co-doped TiO2 rutile (1 1 0) honeycomb structures. The photocatalyst has been prepared by simultaneously oxidizing and doping a Ti-foil substrate at 750 degrees C. The unit cell volume and the crystallite size of grown TiO2 films were measured by Rietveld refinement analysis. The co-doping by boron and nitrogen was achieved simultaneously with the oxidation of the titanium, resulting in a rutile (1 1 0) textured TiO2 film. X-ray photoelectron spectroscopy analysis revealed the presence of Ti-O-N and Ti-O-B-N bonds, and the presence of crystal defects in the lattice was detected and displayed by…
Water Splitting on Multifaceted SrTiO3 Nanocrystals: Computational Study
2021
The financial support of M-ERA.NET2 Sun2Chem project is greatly acknowledged by E.K. Authors thank Dr. Marjeta Ma?ek Kr?manc and prof. Chi-Sheng Wu, for the fruitful discussions. The financial support of FLAG-ERA JTC project To2Dox is acknowledged by Y.A.M. This paper is based upon the work from COST Action 18234, supported by COST (European Cooperation in Science and Technology). The support is greatly acknowledged by Y.A.M. and V.K. The grant No. 1.1.1.2/VIAA/l/16/147 (1.1.1.2/16/I/001) under the activity of Post-doctoral research aid is greatly acknowledged by M.S. and D.B. The Institute of Solid State Physics, University of Latvia (Latvia) as the Centre of Excellence has received fundin…
Enhanced photocatalytic performance of novel electrospun BN/TiO 2 composite nanofibers
2017
International audience; High activity boron nitride/titanium dioxide (BN/TiO2) composite nanofiber photocatalysts were synthesized for the first time via the electrospinning technique. The as-spun nanofibers with a controlled ratio of boron nitride nanosheets (BN) were calcined under air at 500 °C for 4 hours. Their morphological, structural and optical properties were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), BET surface area, Fourier-transform infrared (FTIR), Raman spectroscopy, UV-Visible spectrophotometry and room temperature photoluminescence (PL). The effect of loading different BN sheet amounts on the photocat…