Browsing by Author "Li, W"
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- ItemChemically induced electric field: flat band potential engineering(SPIE, 2012-10-05) Bak, T; Guo, Z; Li, W; Atanacio, AJ; Nowotny, JThe present work considers engineering of the flat band potential, FBP, of metal oxides in a controlled manner. The aim is to minimise the energy losses related to recombination. The related experimental approaches include imposition of a chemically-induced electric field using the phenomena of segregation, diffusion and the formation of multilayer systems. This paper considers several basic phenomena that allow the modification of the surface charge and the space charge at the gas/solid and solid/liquid interfaces. © (2012) Society of Photo-Optical Instrumentation Engineers (SPIE).
- ItemPhotocatalytic properties of TiO2: effect of niobium and oxygen activity on partial water oxidation(Elsevier, 2016-12-05) Li, W; Bak, T; Atanacio, AJ; Nowotny, JThis work reports the effect of niobium (0–1 at%) on photocatalytic activity and the band gap of TiO2 with controlled oxygen activity in the range 10−12 Pa < p(O2) < 105 Pa. It is shown that maximum of photocatalytic performance in partial water oxidation is observed for Nb-doped TiO2 containing 1 at% Nb that is processed at 1273 K in pure oxygen, p(O2) = 105 Pa. The mechanism of photocatalytic water oxidation is considered in terms of a predominant effect of photocatalytically active surface sites corresponding to titanium vacancies. It is shown that the niobium-induced increase of the band gap, surface potential and charge transport have a minor influence on photoreactivity of Nb-doped TiO2 with water. © 2016 Elsevier B.V.
- ItemPhotocatalytic properties of TiO2: evidence of the key role of surface active sites in water oxidation(Americal Chemical Society, 2015-08-21) Bak, T; Li, W; Nowotny, J; Atanacio, AJ; Davis, JPhotocatalytic activity of oxide semiconductors is commonly considered in terms of the effect of the band gap on the light-induced performance. The present work considers a combined effect of several key performance-related properties (KPPs) on photocatalytic activity of TiO2 (rutile), including the chemical potential of electrons (Fermi level), the concentration of surface active sites, and charge transport, in addition to the band gap. The KPPs have been modified using defect engineering. This approach led to imposition of different defect disorders and the associated KPPs, which are defect-related. This work shows, for the first time, a competitive influence of different KPPs on photocatalytic activity that was tested using oxidation of methylene blue (MB). It is shown that the increase of oxygen activity in the TiO2 lattice from 10–12 Pa to 105 Pa results in (i) increase in the band gap from 2.42 to 2.91 eV (direct transitions) or 2.88 to 3 eV (indirect transitions), (ii) increase in the population of surface active sites, (iii) decrease of the Fermi level, and (iv) decrease of the charge transport. It is shown that the observed changes in the photocatalytic activity are determined by two dominant KPPs: the concentration of active surface sites and the Fermi level, while the band gap and charge transport have a minor effect on the photocatalytic performance. The effect of the defect-related properties on photoreactivity of TiO2 with water is considered in terms of a theoretical model offering molecular-level insight into the process. Copyright © 2017 American Chemical Society