Formation of TiO2 nanoribbons by anodization under high current density

Abstract

Highly ordered TiO2 nanoribbons are obtained by anodizations in NH4F electrolyte under high current density. Although intact TiO2 nanoribbons appear, there are still nanotubes beneath nanoribbons. It is reasonable to speculate that TiO2 nanoribbons evolve from TiO2 nanotubes. While the applied current is high, the electronic current is also high, which gives rise to lots of oxygen bubbles. With the accumulation of oxygen bubbles, oxygen bubbles must expand upward and rupture finally. Therefore, gas flow from oxygen bubbles results in the generation of micro-liquid-flow. Because of micro-liquid-flow, the nanotube wall is corroded and scoured. The corrosion of upper pore wall is the most sever and thus the upper pore wall becomes the thinnest locality of nanotube wall. As a result, the nanotubes can collapse easily. Finally, one TiO2 nanotube is divided into several TiO2 nanoribbons while there is still intact tube beneath nanoribbons.