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Title: Synthesis, characterisation and modelling of tungsten(VI) oxide based visible light photocatalysts
Author: Finlayson, A. P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2007
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Alloying of WO3 with Bi2O3 by solid-state inter-diffusion has been studied through the synthesis and characterisation of two intermediate phases, Bi2WO6 and Bi6WO12. Optical measurements indicate that neither compound demonstrates significantly improved visible light absorption compared to Bi2O3 or WO3. Sol-gel synthesis of WO3 using the H2WO4(aq)-ethanol Augustynski method has been investigated via thermal analysis and characterisation of the product films to confirm that conversion to WO3 occurs in the region of 500°C. Heat treatment under nitrogen and the addition of organic amines enabled the synthesis of N doped WO3. Structural characterisation of these films indicated poor crystallisation and the presence of residual organic material. However, optical measurements revealed slight band gap narrowing and the introduction of a second optical transition 0.7 → 2.2 eV in energy. Both the band gap narrowing and the introduction of mid-gap states are predicted by the modelling of N doped WO3 unit cells undertaken using density functional theory. Photoelectrochemical characterisation indicated that this transition does not result in a photocatalytically active state. The H2WO4(aq) sols have been modified with organic additives to exhibit rheological and surface properties suitable for drop-on-demand ink-jet printing. WO3 films printed onto In-SnO2 coated glass have been characterised using morphological, structural, optical and photoelectrochemical techniques. Incident Photon to Current Efficiencies measured from these films (maximum: 35\% at 300 nm) compare well to those manufactured using the more laborious ‘doctor-blade’ method. Thus the utility of ink-jet printing as a rapid, scalable deposition technique for photocatalyst fabrication has been demonstrated.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available