(A) study on the controlled nanostructure and electronic properties of $TiO_2$ nanotubes and their energy storage performances

Abstract

Since the discovery of bundled carbon nanotubes (CNTs) in 1991, one dimensional (1D) nanostructure arrays have received great attention due to not only their unique structural characteristics, but also their remarkable electrical, chemical, and optical properties. Meanwhile, properties of the 1D nanostructure could be strongly dependent on different bonding configurations of their elements. From this point of view, understanding and controlled modification of these bonding configurations are very crucial to achieve the higher performance of the 1D nanostructure. Especially the emerging nanotechnology offers great opportunities to improve the performance of existing energy storage systems. Applying nanoscale materials to energy storage offers a higher capacity compared to the bulk counterparts due to the unique properties of nanomaterials such as high surface areas, large surface-to-volume atom ratio, and size-confinement effect. In particular, 1D inorganic nanostructures like tubes and wires exhibit superior photoelectrochemical characteristics because of the combined advantages of small size and 1D morphology. Also hydrogen and lithium can be stored in different 1D nanostructures in various ways, including physical and chemical sorption, intercalation, and electrochemical reactions. A titanium dioxide ($TiO_2$) material, due to its versatile modification and abundance, has been proposed as one of promising structures for advanced energy storage applications. In this study, nitrogen doping effects on highly aligned $TiO_2$ nanotube arrays with their nanostructural and electronic properties has been studied through experimental and density functional theory calculations. Also their energy storage performance as a photoanode of dye sensitized solar cells (DSSC) and anode material of Li ion secondary batteries were evaluated. Based on calculation results, it was experimentally shown that nitrogen medication in $TiO_2$ nanotubes can be a prospective way for t...