Titanium Dioxide (TiO 2) has been considered an ideal photocatalyst due to
factors such as its photocatalytic properties, chemical stability, impact on the
environment and cost. However, its application has been primarily limited to
ultraviolet (UV) environments due to its high band gap (3.2 eV). This high band
gap limits the harvesting of photons to approximately 4% of sunlight radiation.
Research today is focused on lowering this gap by doping or coupling TiO 2 with
other semiconductors, transition metals and non-metal anions, thereby
expanding its effectiveness well into the visible range.
This thesis explores the effects of thermal and thermochemical ammonia
treatment of nano-particulated TiO 2. The objective is to synthesize a
photocatalytic
activity in the visible range while at the same time retaining its photocatalytic
properties in the UV range. Specifically, this study utilizes pure commercial
nano-particulated TiO 2 powder (Degussa P-25), and uses this untreated TiO2
as
a baseline to investigate the effects of thermal and thermochemical treatments.
Nitrogen-doping is carried out by gas phase impregnation using
anhydrous ammonia as the nitrogen source and a tube furnace reactor. The
effects of temperature, time duration and gas flow rate on the effectiveness of
thermally and thermochemically treated TiO 2 are examined. Thermally treated
TiO 2 was calcinated in a dry inert nitrogen (N2) atmosphere and the effects of
temperature and treatment duration are investigated.
The band gap of the thermally treated and thermochemically ammonia
treated TiO 2 have been measured and calculated using an optical spectrometer.
The photocatalytic properties of all materials have been investigated by the
degradation of methyl orange (MO) in an aqueous solution using both visible
simulated solar spectrum (VSSS) and simulated solar spectrum (SSS) halogen
light sources. Methyl orange degradation has been measured and calculated
using an optical spectrometer. The phase structure and particle size of the
materials is determined using x-ray diffraction (XRD). The BET surface area of
the samples has been obtained using an Autosorb. Surface or microstructure
characterization has also been obtained by scanning electron microscopy (SEM)
and transmission electron microscopy (TEM).
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-4620 |
| Date | 31 October 2007 |
| Creators | Schmidt, Mark |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
| Rights | default |
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