Self-standing TiO2 nanotubular membranes for sustainable production of energy

Synthesis of tubular one-dimensional (1D) nanostructures grown onto the surface of metals (such as Al Ti, W) by electrochemical anodization, have attracted growing scientific interest due to their unique size and shape dependent properties that can be exploited in a wide range of applications [1]. In this context, highly ordered vertically oriented TiO2 nanotubes (TNT) were successful applied as functional materials in the field of photocatalysis, water splitting, gas sensing and solar energy conversion, on the basis of their chemical stability and unique semiconducting properties [2]. In this contribution, we present a simple electrochemical approach to obtain large-area free-standing TNT membranes via a three-step anodic oxidation of pure Ti sheet in fluoride-containing ethylene glycol. The TNT membranes were characterized by Scanning Electron Microscope (SEM), UV-Visible Diffusive Reflectance Spectroscopy, Cyclic Voltammetry and Chronoamperometry. In particular, we report some details related to the synthetic procedure by SEM images of the fundamental steps, evidencing the development of the morphology of the catalytic surface. The study was focused on the ability to control the nanotube morphology, length, pore size, wall thickness and packing degree, by varying some parameters during the synthesis (such as voltage, electrolyte, pH, time of anodization, water concentration, etc.). Finally, the 1D nanostructured films (well-ordered vertically aligned TiO2 nanotubes) were used as electrodic materials for solar devices (DSSC cells, photo-electrochemical cells). Results showed that smooth surface and high aspect ratio TiO2 nanotube (TNT) arrays were fabricated, which may have wide applications in the development of micro-confined reactors for a sustainable production of energy. [1] C. Ampelli, G. Centi, R. Passalacqua, S. Perathoner, Energy Environ. Sci., 3 (2010) 292-301. [2] R. Passalacqua, C. Ampelli, S. Perathoner, G. Centi, Nanosci. Nanotechnol. Lett., 4 (2012), 142-148.