Now showing 1 - 3 of 3
  • 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
  • Publication
    Towards an understanding of the beneficial effect of mesoporous materials on dehydrogenation characteristics of NH3BH3
    Ammonia borane (AB) was loaded onto a range of mesoporous materials (MCM-41, SBA-15 and MCF) by wet impregnation from THF solutions and its thermal dehydrogenation studied using TGA/MS. The interactions between the AB and the surfaces were characterised using difference FTIR spectroscopy. The presence of mesoporous materials promotes lower temperature H2 release, and greater selectivity towards the formation of H2, i.e. decreased formation of gaseous boroncontaining side products. D-FTIR results confirm interactions between isolated silanol groups or surface Si-O-Si species and AB and this supports the proposal that a H-bonding interaction between the surface and deposited AB is important in promoting decomposition at lower temperature. AB interacting with silanol groups decomposes more readily than that coordinated to Si-O-Si. The effect on the temperature of H2 release is greater for materials of larger pore size (rather than materials of larger surface area), i.e. MCF>SBA-15>MCM-41. This suggests that access to the internal surface of the mesoporous material (where the majority of surface silanols are located) is important, and this in turn suggests that polymeric species, which may have restricted access to the internal surface of the different materials, form when AB is dissolved in THF. Decomposition of B-N-containing gaseous materials (to AB(g)) following their formation, on the silanol groups of the SiO2, is suggested as the reason for the increased selectivity of the reaction to H2 (and decreased release of unwanted side products) in the presence of mesoporous material.
      423Scopus© Citations 15
  • Publication
    Co-SBA-15 catalysts in the hydrolysis of NH3BH3 – Influences of Co precursors and catalyst pre-treatment
    H2 was released from ammonia borane (AB) through a hydrolysis reaction over several Co-SBA-15 catalysts. Each catalyst had an induction time prior to becoming active. The activation time related to the in-situ reduction of Co species to an active nano-particulate form and the length of this this induction time varied as a function of the Co-precursor used. The rate of the hydrolysis reaction over the reduced and active catalysts depended on the precursor. While the induction time was not noted in subsequent reactions over the reduced catalysts, the reactivity differences remained. A rationale for the differences based on the preparation steps is suggested
      215Scopus© Citations 5