Date of Award

2007

Degree Type

Thesis

Degree

M.S.

Degree Granting Department

Electrical Engineering

Keywords

Photocatalysis, Methyl orange, Doping, Calcination, Thermal treatment

Abstract

Titanium Dioxide (TiOâ??) 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 TiOâ?? 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 TiOâ??. The objective is to synthesize a photocatalyst with a lower band gap energy that demonstrates 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 TiOâ?? powder (Degussa P-25), and uses this untreated TiOâ?? 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 TiOâ?? are examined. Thermally treated TiOâ?? 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 TiOâ?? 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)