Visible light-activated yellow titanate nanotubes (TNTs) modified by peroxo groups were directly synthesized via a facile chemical reaction route using peroxo titanium complex ions as a precursor. Obtained peroxo-modified TNTs (PTNTs) possessed a cylindrical-shaped tubular morphology with an outer diameter of approximately 10 nm. The peroxo titanium functional group (Ti–O–O) was formed between the interlayers of the lepidocrocite-type titanate crystal that was the base structure of TNTs, with the interlayer distance estimated at approximately 10.02 Å. The formation of the peroxo functional groups reduced the electron density adjacent to the titanium atom, raising the valence band to 1.35 eV and forming a band gap of 2.50 eV, which is lower than that of TNTs (3.19 eV). In addition, the peroxo titanium functional group had a negative potential, which increased the chemical adsorption performances with positively charged rhodamine B molecules in water. Meanwhile, the photocatalytic investigation indicated that the PTNTs have enhanced the photocatalytic performance for RhB decolorization under visible light irradiating in comparison with TNTs. These findings show not only the improvement in the photocatalytic performance but also the potential of processing design by selecting the precursor with arbitrary characteristics.

This study addresses the effects of annealing temperatures (up to 500 °C) on the crystal structure, morphology, and optical properties of peroxo groups (–O–O–) containing titanate nanotubes (PTNTs). PTNTs, which possess a unique tubular morphology of layered-compound-like hydrogen titanate structure (approximately 10 nm in diameter), were synthesized using peroxo-titanium (Ti–O–O) complex ions as a precursor under very mild conditions—temperature of 100 °C and alkali concentration of 1.5 M—in the precursor solution. The nanotubular structure was dismantled by annealing and a nanoplate-like structure within the range of 20–50 nm in width and 100–300 nm in length was formed at 500 °C via a nanosheet structure by decreasing the specific surface area. Hydrogen titanate-based structures of the as-synthesized PTNTs transformed directly into anatase-type TiO₂ at a temperature above 360 °C due to dehydration and phase transition. The final product, anatase-based titania nanoplate, was partially hydrogen titanate crystal in nature, in which hydroxyl (–OH) bonds exist in their interlayers. Therefore, the use of Ti–O–O complex ions contributes to the improved thermal stability of hydrogen titanate nanotubes. These results show a simple and environmentally friendly method that is useful for the synthesis of functional nanomaterials for applications in various fields.