Photoactivation of Surface Peroxides on Titanate Nanotubes

The coexistence of hydrogen peroxide (H₂O₂) and metal oxides accelerates the degradation of organic pollutants by the formation of peroxides on the metal oxide surface. Peroxide-modified titanium oxides are activated by light and exhibit excellent oxidation performance. However, the reaction mechanism has not been fully investigated because the amount of peroxide on TiO₂ is limited. In this study, we developed titanate nanotubes (TNTs) as supports for titanium peroxide formation owing to their large surface area. Treating TNTs with H₂O₂ formed titanium peroxide on their surface while maintaining the nanotube morphology. Peroxide-modified TNTs (H₂O₂-TNTs(<i>X</i>)) exhibited a clear decolorization ability for rhodamine B (RhB) under visible-light irradiation (<i>λ</i> > 420 nm). The reaction rate constant of TNTs treated with a 30 wt% H₂O₂ aqueous solution was 20 times higher than that of pristine TNTs under simulated solar irradiation. During the decolorization of the RhB solution, H₂O₂-treated TNTs selectively deethylated the RhB molecules under visible-light irradiation. Experiments and comprehensive analyses revealed that the deethylation reaction was driven by photogenerated O₂^•-, holes, and photoexcited Ti peroxide species on the H₂O₂-treated TNTs. This study provides an effective strategy for the visible-light-responsive, selective oxidation of organic substrates using H₂O₂.