Visible-light Catalytic Performance of ITO/TiO2 Nanotube Array Composite

Photocatalysis has received extensive attention due to its advantages of mild reaction conditions and direct conversion of solar energy to chemical energy. Improving the solar absorption range and reducing the recombination of photo-generated "electron-hole" pairs are the hot topics in the field of photocatalysis. In this work, the amorphous TiO2 nanotube arrays (TiO2NTs) were prepared by anodic oxidation, and indium-tin (In-Sn) alloy was pressed into the amorphous TiO2NTs by a mechanical hydraulic method to make In9.45Sn1/TiO2NTs, then the In9.45Sn1/TiO2NTs were annealed in air to obtain indium tin oxide (ITO)/TiO2NTs. The photocatalytic properties of the obtained TiO2NTs, In9.45Sn1/TiO2NTs and ITO/TiO2NTs on the removal of methylene blue in aqueous solution were studied and compared. After 180 min visible light irradiation, the degradation efficiency of the ITO/TiO2NTs reaches 96.14%. The applying UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) to explore the optical adsorption abilities of the samples shows the strongest absorbance of ITO/TiO2NTs. Combining the results of transient photocurrent responses, photocurrent density-potential, electrochemical impedance spectroscopy, and Mott-Schottky plots, the ITO/TiO2NTs have higher charge transfer capability and donor density than do other samples, which can reduce the recombination of holes and electrons, thus improving the visible-light catalytic performance. After five cycles, the degradation rate of the ITO/TiO2NTs still maintains 90.28%. Results of free radicals trapping experiments reveal that center dot O-2(-) and center dot OH are the main active substances for the photocatalytic degradation.