Abstract
Heterogeneous photocatalysis is the acceleration of a photoreaction in the presence of a semiconductor, whereby, the semiconductor absorbs the photon energy to create charge carriers which may take part in redox reactions at the surface of the semiconductor. Photocatalysis has been investigated for the conversion of solar energy to fuels i.e. water splitting for hydrogen and carbon dioxide reduction to solar fuels. Also, photocatalysis has been widely investigated for the remediation of polluted air and water. The major challenge for solar photocatalysis is the requirement for the semiconductor to utilise the solar spectrum efficiently. To date, most photocatalytic materials work efficiently only in the UV domain.In this work, novel clusters modified titania materials were investigated for the enhanced photocatalytic solar energy harvesting efficiency. Additionally, the rate of photocatalytic degradation of pollutants was compared to the photoelectrochemical measurements for several commercial titanium dioxide nanoparticles.
The first part of the research deals with the correlation between the photocatalytic activity with the analytical properties and photoelectrochemical measurements. A range of commercial TiO2 nanoparticles were spray-coated onto Ti foil and, used as photoanodes to determine the photocurrent and open circuit potential under irradiation. This data was compared to photocatalytic degradation rate for formic acid and phenol using the same nanomaterials. The open circuit potential under irradiation provides better correlation to the observed photocatalytic degradation rate data for both phenol and formic acid as compared to the photocurrent. This is because under open circuit condition the photoelectrode is behaving like an immobilised photocatalytic system.
In the second part of the project, copper clusters were prepared by adopting BrustSchiffrin (BS) and electrochemical (EC) synthesis protocols. The average particle sizes of the clusters were 0.9 and 0.58 nm for BS and EC copper clusters as measured by scanning transmission electron microscopy. The prepared clusters were Cu0/Cu+ as measured by X-ray photoelectron spectroscopy.
The prepared copper clusters were loaded on the surface of various titanium dioxide materials using spray coating. The TiO2 materials employed in this study included commercial TiO2 nanopowders, thermally grown films and electrochemically anodised aligned nanotubes. The copper loaded titanium dioxide materials demonstrate some additional states near the valence band edge of the materials, indicative of possible band-gap narrowing, measured by valence band X-ray photoelectron spectroscopy and UV-vis spectroscopy. The spray coated materials were investigated for their photoelectrochemical response using chopped linear sweep voltammetry, photocurrent at fixed potential and photocurrent action spectral responses. The titania nanomaterials demonstrate enhancement in the photocurrent response under UV-vis irradiation. The titanium dioxide surface modification with BS copper clusters show some visible light activity. The Cu-P25 demonstrated 4-fold enhancement in the photocatalytic CO2 reduction for CH4 production yield in a gas phase reactor.
| Date of Award | Oct 2017 |
|---|---|
| Original language | English |
| Sponsors | Vice Chancellor's Research Scholarship (VCRS) |
| Supervisor | John Byrne (Supervisor) |
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