Synergistic role of self-induced CdIn2S4 nanopyramid sacrificial layer for the enhanced photocatalytic activity of TiO2 nanotube-based chalcogenide heterostructures

Abstract

A simple treatment was employed to obtain a novel design of a highly stable visible light responsive In₂S₃/CdS/TiO₂ nanotube-based photocatalyst for H₂ production. At first, In₂S₃/CdS/TiO₂ nanotubes were fabricated by incorporating CdS and In₂S₃ quantum dots (QDs) onto TiO₂ nanotubes (TNTs) via a chemical bath deposition method. In the second step, a portion of the QDs layer (CdS and In₂S₃) was converted into a layer of CdIn₂S₄ pyramid-like structure by thermal treatment of In₂S₃/CdS/TNTs in an Ar environment (Ar-In₂S₃/CdS/TNTs). The photocatalytic performances of the different heterostructure assemblies (simple and Ar-treated samples) were tested. The incorporation of CdS and In₂S₃ QDs significantly improved the visible response, showing higher photocurrent density and H₂ production rate (0.5694 mL h⁻¹ cm⁻²) values. Furthermore, the outer layer of CdIn₂S₄ improved the photostability of In₂S₃/CdS/TNTs and further boosted the H₂ evolution rate (0.6281 mL h⁻¹ cm⁻²). The apparent quantum yields (AQYs) of Ar-In₂S₃/CdS/TNTs at 450 nm and 632 nm LED were 5.54% and 13.57%, respectively. The higher photocurrent density and lower charge transfer resistance suggest that the structure of the Ar-In₂S₃/CdS/TNTs photoanodes provides efficient charge carrier separation and interfacial charge transport properties. Dye degradation of methylene blue using Ar-In₂S₃/CdS/TNTs showed complete degradation of the dye within 22 min, which was 5 minutes lesser than that observed for In₂S₃/CdS/TNTs.