Comparison of photoelectrochemical properties of TiO2-nanotube-array photoanode prepared by anodization in different electrolyte

Self-organized, well-crystallized and high aspect-ratio TiO₂ nanotube arrays (TNAs) have been prepared by anodic oxidation in dimethyl sulfoxide (DMSO) containing 5 wt% HF at 40 V (vs. Pt). A 50 h anodization results in a nanotube arrays approximately 19.4 μm in length, referred as long tube. As a comparison, the short titania nanotube arrays, about 500 nm in length, was obtained by anodization in HF aqueous solution, referred as short tube. Different characterization techniques (viz. FESEM, TEM, XRD and DRS) are used to study the nanotubular microstructure. The morphology of the nanotube electrodes shows an evident influence on their photocatalytic (PC) and photoelectrochemical reactivity. The long tube reveals enhanced photocurrent response and PC degradation efficiency of organic compounds. The kinetic constant of PC degradation of methylic orange (MO) for long tube electrode is found 1.55 times as high as the short tube. A significant photoelectrochemcial synergetic effect in MO degradation was observed on the long tube electrode and the photoelectrocatalytic (PEC) degradation of MO on long tube is 27% higher than its PC process.