Photoelectrochemical performance of TiO2 nanotube arrays by in situ decoration with different initial states

Here, carbon dots (CDs) only or nanocomposites of CDs and TiO2 (CDs–TiO2) were used to decorate titanium dioxide nanotube arrays (TiO2NTs) in situ by solvothermal method. Two initial states of TiO2NTs were prepared for contrast, including the amorphous TiO2NTs (TiO2NTs-0) just experienced anodic oxidation process and that further calcined TiO2NTs (TiO2NTs-450). It was found that the newborn CDs or CDs–TiO2 were more likely to anchor on TiO2NTs-0 than the calcined TiO2NTs-450, and more Ti–C bonds were found in the composites which were derived from TiO2NTs-0 after the solvothermal treatment. An evident photocurrent could be demonstrated for either CDs or CDs–TiO2 decorated TiO2NTs once exposed to visible light. And CDs–TiO2NTs-0 showed the highest photocurrent density (4.51 µA·cm−2). However, the results of photodegradation measurements revealed that CDs–TiO2 decorated TiO2NTs with different initial states (especially CDs–TiO2–TiO2NTs-0) showed more excellent photocatalytic activity under both ultraviolet (UV) and visible light illumination.