Optimized Spacing between TiO2 Nanotubes for Enhanced Light Harvesting and Charge Transfer

Abstract

We investigate two distinctly different anodic TiO2 nanotubular morphologies, spaced and close-packed arrays. While the close-packed tubular arrays are formed in ethylene glycol, spaced nanotubes (NTs), which have a regular gap between individual NTs, grow in a diethylene glycol or dimethyl sulfoxide-based electrolyte. Depending on the electrolyte used for anodization, the morphology, crystal structure, and chemical composition of the resulting nanotubular layer vary from one another. This influences the electrochemical and photoelectrochemical activity of the NTs. Overall, we find that spaced NTs can not only provide enhanced charge-transfer characteristics but can also show beneficial light absorption characteristics when used as a photo- or light-harvesting electrode.