2011 YÜksek lisans tez özetleri

Investıgatıon Of The Photoelectrochemıcal Actıvıty Of Tıtanıum Dıoxıde Nanotubes

Photoelectrochemical systems are the system which being developed for the conversion of solar energy into hydrogen and consist of a semiconductor electrode in contact with an aqueous electrolyte. When thesemiconductor is irradiated with light greater than its bandgap, photoinduced charge separationoccurs in the electrode and this process result in a photocurrent in the cell. This photocurrent splits water into hydrogen and oxygen at separate electrode surfaces. Generation of hydrogen using solar energy and water in a photoelectrochemical system is the most promising method to acquire alternative and renewable energy. A major challenge to the use of photoelectrochemical cells in the production of hydrogen from water and solar energy is the low photoanode efficiency.

TiO₂ is especially attractive as a photoelectrode because of its high efficiency, resistance to corrosion, chemical stability, environmental compatibility and its high surface area. Because TiO₂ is a large band gap it absorbs only solar light in the UV region. To improve the photoelectrochemical efficiency, researchers have adopted different strategies such as changing the electrical properties of TiO₂ by varying the crystallite size, doping TiO₂ with metal/nonmetal ions or coupling it with a low band gap semiconductor material to extend the optical absorption into visible region.

In this thesis titanium dioxide nanotubes fabricated by anodic oxidation of titanium foil and investigated photoelectrochemical activity by voltametry technics such as lineer sweep voltametry, cyclic voltametri under light and dark. Light absorption properties and activity of TiO2 nanotubes enhanced by doping metal-sulphur composites. The structural and optical properties of these materials were characterized by using SEM, XRD and DRS analysis

TiO₂ nanotube arrays are modified with ZnS, NiS and CdS doping by using SILAR method (Successive İonic Layer Adsorption and Reaction). Modification of the TiO₂ nanotubes resulted in an increase in the visible light adsorption and increase in photocurrent response. The highest photocurrent density is 130 µA/cm² obtained from intrinsic TiO₂ nanotubes. CdS/TiO₂ nanotube showed the highest fotocurrent density under visible irradiation and 3,1 mA/cm² photocurrent density were obtained from CdS/TiO₂ nanotubes at same concentration of other metal-sulphur compounds. Therefore TiO₂ nanotubes were modified at different concentration of CdS. Also charge carrier density of intrinsic TiO₂ nanotube and CdS/TiO₂ nanotubes were determined by Mott Schottky plot.
  
  

GÜRŞEN Sibel

Danışman : Doç. Dr. Hüseyin Deligöz

Anabilim Dalı : Kimya Mühendisliği

Programı : Kimyasal Teknolojiler

Mezuniyet Yılı : 2011

Tez Savunma Jürisi : Doç.Dr. Hüseyin Deligöz

Prof. Dr. Gülten Gürdağ

Doç. Dr. Tülin Banu İyim

Doç. Dr. Gamze Güçlü

Yrd. Doç. Dr. Saffettin Yıldırım