31113-52-7Relevant articles and documents
Visible light photo-oxidation of model pollutants using CaCu 3Ti4O12: An experimental and theoretical study of optical properties, electronic structure, and selectivity
Clark, Joanna H.,Dyer, Matthew S.,Palgrave, Robert G.,Ireland, Christopher P.,Darwent, James R.,Claridge, John B.,Rosseinsky, Matthew J.
supporting information; experimental part, p. 1016 - 1032 (2011/04/15)
Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu3Ti4O12 has distinct octahedral Ti4+ and square planar Cu2+ sites and is thus a candidate material for this approach. The sol-gel synthesis of high surface area CaCu3Ti4012 and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO4 units within the structure of CaCu3Ti4O12) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu 3Ti4O12 which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts.
Electron-transfer oxidation of chlorophenols by uranyl ion excited state in aqueous solution. Steady-state and Nanosecond flash photolysis studies
Sarakha, Mohamed,Bolte, Michele,Burrows, Hugh D.
, p. 3142 - 3149 (2007/10/03)
The oxidation of chlorophenols by photoexcited uranyl ion was studied in aqueous solution at concentrations where the ground-state interactions were negligible. Nanosecond flash photolysis showed that a clean electron-transfer process from the chlorophenols to the excited uranyl ion is involved. This is suggested to lead to the formation of a U(V)/chlorophenoxyl radical pair complex. The efficiency of this charge-transfer process is unity for the three chlorophenols. However, low product yields suggest that in the absence of oxygen, back electron transfer, both within the radical pair and from separated uranium(V) to phenoxyl radicals, appears to be the major reaction pathway. In the presence of oxygen the quantum yields of disappearance of chlorophenol and of photoproduct formation increased. This leads to the conclusion that oxygen favors reaction with uranium(V) and/or the uranium(V) - phenoxyl radical pair, leading to the formation of the superoxide anion and its conjugate acid, HO2*, which then regenerate UO22+. Based on this, a catalytic cycle for chlorophenol photooxidation involving uranyl ion and molecular oxygen is proposed.
