TiO₂ nanotube/ZnIn₂S₄ nanoflower composite with step-scheme heterojunction for efficient photocatalytic H₂O₂ production and organic dye degradation

The intellectual design of photocatalysts to advance important photocatalytic goals such as pollutant degradation and hydrogen peroxide production is challenging. In the present work, a novel TiO₂ NT/ZIS heterojunction photocatalyst was synthesized by a hydrothermal method and applied for photocatalytic RhB degradation and H₂O₂ generation. Prepared materials were characterized by different techniques concerning structural, optical, morphological, and electrochemical properties. At the same time, the electronic-structural features and photocatalytic mechanism were profoundly investigated by combining Tauc plots, Mott-Schottky curves, XPS analysis, and scavenging test results. The TiO₂ NT/ZIS heterojunction displayed the best activity in H₂O₂ generation of 9.78 mmol/L after 30 min, which was about 5.1, 2.1, and 1.8 times higher than those of pure P25, TiO₂ NT, and ZIS samples, respectively. In addition, the RhB degradation efficiency reached 90.2% on TiO₂ NT/ZIS nanocomposite after 120 min, while 18.2%, 37.4%, and 38.6% on pure P25, TiO₂ NT, and ZIS, respectively. An S-scheme mechanism was suggested to model and interpret the improved photocatalytic performance of the TiO₂ NT/ZIS heterojunction composite. This work provides guidance for the design, development, and application of heterostructure photocatalysts in H₂O₂ production.