Controlled spacing of self-organized anodic TiO2 nanotubes

Abstract

We report on how to grow and control self-organized TiO2 nanotube arrays that show defined and regular gaps between individual nanotubes. For this we use electrochemical anodization of titanium in fluoride containing di-ethylene glycol (DEG) electrolytes, with variations in voltage and water content in the electrolyte. In these specific electrolytes, such nanotubes show a true spacing, i.e. nanotubes are spaced both at top and at bottom in regular intervals, this in contrast to classic nanotubes obtained in other organic electrolytes showing a close-packed organization. We identify critical parameters, that define the region of existence i.e. under which condition tube spacing occurs as well as the intertube distance, to be the voltage and the water content. Using these findings allows to grow tubes where diameter and spacing can even be independently controlled

Fast growth of TiO 2 nanotube arrays with controlled tube spacing based on a self-ordering process at two different scales

“…To evaluate the impact of the optimized electrolyte [15] on nanotube growth, we performed systematic investigations in a DMSO electrolyte containing 4 wt% HF, 1 wt% H2O and 0.3 wt% NH4F while varying the voltage and temperature. The slow-growing NTs (initial conditions) were fabricated in a DMSO electrolyte containing 2 wt% HF at 30 V (at 30°C) for 1 h. Typical current density-time (J-t) curves are shown for two cases (initial conditions and after optimization) in Figure 2(a).…”

“…However, only a few experimental approaches report tube layers with a true and controllable inter-tube spacing over the entire tube length. One method of producing regular arrays of individual tubes with control over the tube-to-tube distance uses DEG electrolytes [15]. A second electrolyte class that can be used to achieve such spacing is DMSO [10].…”

Enhanced Electrochemical Performance of Electropolymerized Self-Organized TiO2 Nanotubes Fabricated by Anodization of Ti Grid

“…A large irreversible capacity observed at the first cycles is attributed to the side reaction of Li + and the presence of residual water at the surface of TiO 2 nts and in the polymer electrolyte. Additionally, some Li ions are trapped inside the TiO 2 lattice structure after the first Li + insertion, thereby reducing the capacity of the cell [35,50]. Nevertheless, for the subsequent cycles the capacities can be stabilized, the discharge capacity values recorded in the 2nd and 3rd cycles are 382 and 380 µAh cm −2 with improved coulombic efficiency of 98.4 and 98.7%, respectively.…”

“…% NH 4 F, and 2 wt. % water [35]. All the anodization experiments were carried out at room temperature in a two-electrode system with a Ti grid as a working electrode and platinum (Pt) foil as a counter electrode.…”

Spaced Titania Nanotube Arrays Allow the Construction of an Efficient N‐Doped Hierarchical Structure for Visible‐Light Harvesting

“…The individual NTs have a length of 3 μm and a diameter of 170 nm. It is apparent that each NT is separated from the others, leaving a space of approximately 200 nm between individual tubes . This distance is used to decorate the individual NT walls with TiO 2 NPs by using a TiCl 4 hydrolysis approach .…”