One-Step Hydrothermal Synthesis of Anatase TiO 2 Nanotubes for Efficient Photocatalytic CO 2 Reduction.

The hydrothermal dissolution-recrystallization process is a key step in the crystal structure of titania-based nanotubes and their composition. This work systematically studies the hydrothermal conditions for directly synthesizing anatase TiO 2 nanotubes (ATNTs), which have not been deeply discussed elsewhere. It has been well-known that ATNTs can be synthesized by the calcination of titanate nanotubes. Herein, we found the ATNTs can be directly synthesized by optimizing the reaction temperature and time rather than calcination of titanate nanotubes, where at each temperature, there is a range of reaction times in which ATNTs can be prepared. The effect of NaOH/TiO 2 ratio and starting materials was explored, and it was found that ATNTs can be prepared only if the precursor is anatase TiO 2 , using rutile TiO 2 leads to forming titanate nanotubes. As a result, ATNTs produced directly without calcination have excellent photocatalytic CO 2 reduction than titanate nanotubes and ATNTs prepared by titanate calcination.