Graphite-like carbon branched $TiO_2$ Nanotube Photocatalyst : Fabrication and analysis

Abstract

As shortage of fossil energy, the numerous research for alternative energies such as hydrogen, wind and solar are performing for solve our dependence on fossil fuels. Among these candidates of alternative energy, hydrogen is regarded the most possible one with increase of conversion efficiency of fuel cells. Moreover, photogenerated hydrogen via photocatalyst and natural sunlight from water has opened up infinite possibilities about non-polluting, re-use and no-limit energy because byproducts of fuel cells are water and oxygen since electrochemical photolysis phenomena discovered. Because $TiO_2$ has proper conduction band level for hydrogen generation, high photooxidation reaction potential, no photocorrosion, excellent durability and economical advantage when compared with other photocatalyst, it is still remain as one of the powerful photocatalyst until these days. However, due to very slow interfacial electron transfer time than electron-hole recombination, only very few of photoexcited electrons from $TiO_2$ can combine with hydrogen cations and it leads to low quantum efficiency of hydrogen generation. In this work, we adopt two technologies for reduce electron-hole recombination phenomena. (i) Na-nosize effect: nanosized $TiO_2$ remarkably decreases the probability of electron-hole recombination because the distance between reaction part with hydrogen cations and site of photoexcited electrons become short as atomic range. (ii) Electron sink via conductive carbon materials: Conductive carbon allotropes-$TiO_2$ composites show improved $TiO_2$ photocatalytic performance because they formed semiconductor-metal junction called as Schottky barrier and photoexcited electrons from conduction band of $TiO_2$ have driving force to transfer toward carbon allotropes. Firstly, We fabricated highly ordered and vertically aligned $TiO_2$ nanotube arrays by anodization method. The morphology of anodized $TiO_2$ nanotubes is open tip and closed bottom structure with...