Graduation Year

2007

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Elias Stefanakos, Ph.D.

Co-Major Professor

D. Yogi Goswami, Ph.D.

Committee Member

Nikolai Kislov, Ph.D.

Keywords

photocatalysis, methyl orange, doping, calcination, thermal treatment

Abstract

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).

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