Enhancing energy harvesting and conversion efficiencies of heterogeneous photocatalysts for solar water splitting using surface plasmon resonance and cathodic reduction methods

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
University of Alabama Libraries

This dissertation presents surface enhanced photocatalytic characteristics of heterogeneous catalysts (e.g., α-Fe2O3 and CdS) for solar water splitting. The enhancement can be obtained by either incorporating plasmonic metallic nanostructures, such as Au nanorods (NRs), or cathodic reduction of catalytic materials. This dissertation also presents various electrochemical methods for large-scale synthesis of plasmonic structures (e.g., vertically aligned NRs) for surface enhanced photoelectrochemistry. Four major aspects of the dissertation are described briefly. First, surface-enhanced light absorption and photoelectrochemical characteristics of α-Fe2O3 thin film modified with Au NRs in a top configuration are studied. The photoelectrochemical reaction of the plasmon active substrates for water oxidation is performed and compared at various α-Fe2O3 thicknesses. The photocurrent increase in the surface plasmon region is attributed to the enhanced visible light absorption of α-Fe2O3 in the presence of Au NRs. Second, a template-free technique is invented for a facile fabrication of vertically standing metal NRs and nanowires (NWs). The growth mechanism of NRs and NWs is explored through investigating their morphological changes as the electrodeposition proceeds. Because of their large specific surface area, one direction alignment, stability, and wide tunability over the diameter, length, and coverage, these NRs and NWs will have broad applications in surface enhanced photoelectrochemical reaction and optical spectroscopy. Third, cathodic reduction methods are introduced and they are capable of improving the photoelectrochemical performance of α-Fe2O3 photoanode. The morphology and photoelectrochemical responses of α-Fe2O3 thin-film photoanode are presented before and after the cathodic reduction. The photocurrent of ~20 nm α-Fe2O3 thin film is enhanced by about 7 times after the cathodic reduction. The enhancement is attributed to the conductivity improvement. Finally, vertical-aligned Ag nanoplates and NWs are presented at the outlet of this dissertation. These nanostructures are electrochemically deposited on Indium Tin Oxide (ITO) substrates with the assistance of sacrificial templates such as anodic aluminum oxide (AAO) templates. Ag nanostructures obtained using this method have minimum contamination because no surfactant is adopted for the synthesis; therefore they are suitable for surface modifications for applications in surface-enhanced Raman scattering, surface-enhanced photocatalyst, and metal-enhanced fluorescence.

Electronic Thesis or Dissertation
Chemistry, Analytical chemistry