Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Synthesis of Nanosize Mixed Oxides of Distinct Shapes and Investigation of

Their Photocatalytic Activities
Today, the worldwide depletion of energy resources and environmental pollution are the most important problems threatening human life. Within the recent scientific studies dealing with these problems, the photocatalytic degradation of toxic organic substances in water and the photoelectrochemical hydrogen production are attracting too much attention. All of these studies are based on the heterogeneous photocatalytic processes using the semiconductor materials activated with visible light energy in the form of radiation.
In this study, one-dimensional TiO₂ nanorod structures, that have ease of separation from the reaction media and showing high photocatalytic activity ensuring that the facilitated electron transitions, were synthesized on the conductive glass substrate (FTO glass) as thin films for use in heterogeneous photocatalytic processes.
To investigate the effect of the synthesis conditions of TiO₂ nanorod array thin films, pure TiO₂/FTO samples were synthesized at various synthesis conditions by the hydrothermal method. Synthesized TiO₂ nanorod array thin films were modified with various metal solutions (Cu²⁺, Ni²⁺, Co²⁺), in addition to Pt⁰, with CdS and with different anions (B, C, N, S). Synthesized film samples were characterized by XRD, UV-vis DRS, SEM, PL spectroscopy, contact angle measurements and ICP-MS analysis. TiO₂/FTO samples that synthesized at different conditions were tested by using, a model organic dye, methylene blue degradation under UV illumination. The sample that showed the highest photocatalytic activity in these tests was used for the further modifications. The photocurrent densities of the modified TiO₂/FTO nanorod film samples were measured and the charge carrier densities were calculated as parameters for photoelectrochemical hydrogen generation capacity. Furthermore, the photocatalytic activities of these modified samples were investigated for methylene blue degradation under visible light.
TiO₂/FTO nanorod film synthesized with HCl:H₂O=1:1 and 1.0 ml TiCl₄ at 180°C for 2 hours, showed 93.53% conversion under UV illumination. Modified TiO₂/FTO samples had lower band gap energies and they showed higher activity than pure TiO₂/FTO even under visible light illumination. The samples that showed the highest photocurrent densities are of 10Pt⁰-50Ni²⁺-TiO₂/FTO and 25CdS-TiO₂/FTO. They showed approximately 1.36 mA/cm² photocurrent density and 80% conversion of methylene blue under visible light.