Hierarchically organized titanium dioxide nanostructured electrodes: Quantum-sized nanowires grown on nanotubes

Titanium dioxide nanotube electrodes were fabricated by anodization of titanium and decorated with quantum-sized rutile nanowires (2 nm in diameter) by chemical bath deposition. The length of the nanotubes (120 nm in external diameter) was varied between 4 and 10 μm by changing the anodization time. The hierarchically organized electrodes present good mechanical properties and an enhanced capacity for reversible charge accumulation. The photoelectrocatalytic properties of such electrodes have been tested by photo-oxidizing both water and oxalic acid, turning out to be superior to those of bare nanotubes, which are ascribed to an enhanced interfacial area while keeping the favorable transport properties (for both electrons and chemicals) typical of nanotube electrodes.