Investigation of the synthesis and multifunctional use of TiO2 containing nano-structured materials by hydrothermal method

Recently, research and development activities on alternative energy sources and systems are among the priority research topics of many countries. Supercapacitors are one of the promising new areas to meet this energy need. Especially metal oxides are very interesting in this field. TiO2 is a unique non-toxic semiconductor with many applications. 3D TiO2 metal oxide nanostructures to be obtained on pollen microcapsules and their Ni doped ones were hydrothermally produced within the scope of this thesis. The use of the produced materials in the field of energy technologies and in photocatalytic applications have been investigated. First, sporopolen exine capsules (SEK) were obtained from Pistacia pollen by acidolysis method. Then, to be used as electrode active material, SEKs were coated with TiO2 and Ni-TiO2 by hydrothermal method and hollow 3D spherical powders were obtained. These materials were designed as supercapacitor electrodes. In addition, 3D pollen-containing electrodes on Ni foam were produced by using the hydrothermal method. While the structures grown on Ni foam allow direct use as electrodes without the need for any organic binders and conductivity enhancers, it has also been determined that their electrochemical performance is much better than powder electrodes. In particular, the TiSEK/NF-430 electrode showed a maximum specific capacitance of 311.15 F/g at a constant current of 5 A/g, while the Ni1TiSEK-430/NF showed a maximum specific capacitance of 733 F/g at a constant current of 20A/g. In addition, TiSEK/NF-430//AC asymmetrical supercapacitor device design, which makes 20,000 charge-discharge cycles in the potential window of -0.2 V to +1.5 V, was also carried out. In photocatalytic studies, it was determined that TiPistSEKs were inactive under visible light, but photoactive under UV. NiTiSEK microcapsules formed by Ni doping were photoactive under both UV and visible light. Keywords: metal oxide; supercapacitor; sporopollenin; nanostructure; photocatalysis