GEOMETRY AND MORPHOLOGY OF TiO2 AND Fe2O3 NANOTUBES FOR SOLAR PHOTOLYSIS OF WATER

Abstract

In this work, self organized and vertically oriented double walled TiO2 nanotubes and thin walled α- Fe2O3 nanotubes were synthesized for visible light driven photocatalytic water splitting. Sonoelectrochemical anodization technique in combination with a room temperature ionic liquid was utilized to synthesize concentric nanotubes. Nanotubes grown by this method had external diameters around 82 and 206 nm. Compared to similar single walled TiO2 nanotubes and nanoparticles, these third generation nanotubes showed two to four fold greater photoactivity. It was found that the nanotubes show 18% visible light activity under simulated solar light. The nitrogen annealed samples showed highest photocatalytic activity when compared to oxygen and hydrogen annealed samples. The structural properties of these novel structures have been studied extensively. In addition to this, smooth and ultra thin walled α- Fe2O3 nanotubes were synthesized using a sonoelectrochemical anodization technique. A photocurrent density of 1.41 mA/cm2 was observed for hematite nanotube arrays with more than 50% being contributed by the visible light components of the solar spectrum. These types of stable and environmentally compatible novel structures can be recognized as a breakthrough in the hydrogen generation research.