Self-ordered Nanotubular TiO2 Multilayers for High-Performance Photocatalysts and Supercapacitors

Arrays of multilayered TiO2 nanotubes are successfully fabricated by anodizing commercial Ti foils with multi-pulsed voltage waveforms. The fabricated structures feature an interesting multilayered morphology with each layer consisting of self-ordered TiO2 nanotubes (diameter of tens of nanometers and length of several hundred nanometers) aligned vertically to the Ti substrate, and the possible growth mechanism is proposed. The novel multilayered TiO2 nanotubes exhibit significantly enhanced photocatalytic efficiency than the conventional TiO2 nanotubes and the multilayered nanoporous TiO2 structures previously reported by our group. Moreover, the multilayered TiO2 nanotubes are for the first time investigated for supercapacitor applications, enabling superior capacitance and good cycling stability: the specific capacitance of the C-modified multilayered TiO2 nanotubes is ∼60 times higher than the pristine multilayered TiO2 nanotubes, and ∼1.6 times of the C-modified single-layered TiO2 nanotubes.