Recent Advancements in Morphologies of TiO2 Nanotube Layers and Their Photocatalytic Performance

Abstract

Self-organized TiO2 nanotubes arrays, formed by electrochemical anodization of Ti, have attracted tremendous scientific and technological attention, due to their remarkable properties such as the tunability of dimensions, their directionality, high surface area, low density, and ability to absorb significant amount of incident light [1,2].The most widely used electrolyte for the synthesis of TiO2 nanotube layers is based on ethylene glycol containing small amounts of water and fluoride ions. However, nanotubes prepared in these electrolytes present a double-walled structure, with the outer wall consisting of almost pure TiO2 and the inner wall consisting of TiO2 contaminated with carbon and fluoride species [3,4]. In the recent years, the selective etching of the inner nanotube wall on Ti layer enabled synthesis of single-wall nanotubes that showed a superior photo-electrochemical performance compared to their double-walled counterparts [5]. An extensive etching enabled also the synthesis of single tube powders, which could be effectively decorated with Fe3O4 nanoparticles to act as magnetically guidable photocatalyst [6,7].The presentation will focus on the influence of all these nanotube morphologies on the photocatalytic degradation in the liquid phase. In particular, we will discuss, how the annealing temperature of single nanotubes influences their photocatalytic performance [7] and how the wall thickness of the single wall nanotubes can be optimized for the best performance [8]. Experimental details and photocatalytic results will be presented and discussed.