Now showing 1 - 4 of 4
  • Publication
    Carbon-Doped TiO2 and Carbon, Tungsten-Codoped TiO2 through Sol-Gel Processes in the Presence of Melamine Borate: Reflections through Photocatalysis
    A series of C-doped, W-doped, and C,Wcodoped TiO2 samples have been prepared using modified sol-gel techniques. Reproducible inexpensive C-doping arises from the presence of melamine borate in a sol-gel mixture, whereas W-doping is from the addition of tungstic acid to the sol. The materials have been characterized using elemental analysis, N2 physisorption (BET), thermogravimetric analysis, X-ray diffraction, Raman, X-ray photoelectron, UV-vis spectroscopies, and photocatalytic activity measurements. Doping C and W independently results in an increased absorbance in the visible region of the spectrum with a synergistic effect in increased absorbance when both elements are codoped. The increased visible-light absorbance of the W-doped or codoped materials is not reflected in photocatalytic activity. Visiblelight- induced photocatalytic activity of C-doped material was superior to that of an undoped catalyst, paving the way for its application under only visible-light irradiation conditions. A significant fraction of the spectral red shift commonly observed with doped catalysts might be due to the formation of color centers as a result of defects associated with oxygen vacancies, and bandgap-related narrowing or intragap localization of dopant levels are not the only factors responsible for enhanced visible-light absorption in doped photocatalysts. Furthermore, bandgap narrowing through increases in the energy of the valence band may actually decrease photo-oxidation activity through a curtailment of one route of oxidation.
      871Scopus© Citations 108
  • Publication
    Visible light active C-doped titanate nanotubes prepared via alkaline hydrothermal treatment of C-doped nanoparticulate TiO2: Photo-electrochemical and photocatalytic properties
    Carbon-doped titanate nanotubes (C-TNT) were formed via alkaline hydrothermal treatment of a TiO2 nanoparticulate material pre-doped with carbon. Attempts to form C and W co-doped titanate nanotubes using analogous C and W co-doped nanoparticulate materials were unsuccessful. Physical characterisations, such as X-ray diffraction, N2 physisorption and Transmission Electron Microscopy, confirmed the formation of titanate nanotubes ~7 nm in diameter and hundreds of nm in length with increased surface areas relative to the nanoparticulate precursors. X-ray Photoelectron Spectroscopy confirmed the retention of substitutional carbon dopant and the exclusion of tungsten dopant from the doped TNT materials. Converting doped (or undoped TiO2) into C-TNT (or TNT) slightly increases the material’s bandgap but the C-TNT material (in contrast to TNT and undoped TiO2) absorbs into the visible region of the spectrum. C-doped and un-doped titanate nanotube materials were more active in promoting the photo degradation of 4-chlorophenol under visible light than their analogous nanoparticulate precursors. C-TNT was the most photocatalytically active material tested. However, photocurrent response measurements showed C-TNT to be less effective at generating current following irradiation than both its nanoparticulate analogue and nanoparticulate P25 when screen printed onto electrode surfaces. We ascribe this to non-optimal alignment of the TNTs on the electrode surface.
      624Scopus© Citations 33
  • Publication
    Visible Light-Driven Gas-Phase Artificial Photosynthesis Reactions over Ruthenium Metal Nanoparticles Modified with Anatase TiO2
    Ruthenium metal nanoparticles with a narrow size distribution have been synthesised via a solvothermal method. The solids were characterised using a range of analytical techniques (XRD, TEM, TPD, and XPS) and tested in the CO2+H2O reaction under simulated solar radiation, showing photocatalytic activity towards the production of CH4 and CO. The photocatalysis was promoted through a plasmonic excitation of the Ru. The addition of Ti to the preparation resulted in the formation of anatase TiO2. Notwithstanding the fact that the energy of the light used during the photocatalysis was insufficient to excite TiO2, its presence affects the catalysts’ optical and chemical properties and the product (CH4/CO) ratios, favouring the evolution of CO over that of CH4 (suggesting exciton transfer to TiO2 from plasmonically excited Ru).
      386Scopus© Citations 2
  • Publication
    Routes to visible light active C-doped TiO2 photocatalysts using carbon atoms from the Ti precursors
    In this work, different thermal treatments of titanium isopropoxide-derived photo-catalyst precursors, designed with the purpose of generating C-doped TiO2 photo-catalysts using carbon atoms present in the TiOx gel precursors as dopants, are presented. Specifically, these look at varying the standard calcination techniques using heat treatments in He (rather than calcination in air) and lower temperature calcinations (200 °C rather than 500 °C). The formed materials are characterised using N2 physisorption, XRD, UV Visible spectroscopy and XPS and their activities in promoting the oxidation of 4-chlorophenol under visible-light-only conditions were analysed. The nature of carbon remaining on the (or in the) material is discussed found to be both surface graphitic carbon and carbon present in anionic dopant positions. The different contributions of each type of carbon to the catalytic photo-activity under visible light are discussed.
      411Scopus© Citations 25