Visible active narrow/narrow band gap CuO/Cu₂SnS₃ nanoheterostructures as efficient nanophotocatalysts

Binary metal oxide/ternary metal sulphide based nanoheterostructures, such as CuO/Cu₂SnS₃, were prepared via a modified hydrothermal route. The prepared nanoheterostructures were characterized using scanning electron microscopy, x-ray powder diffractometer, XPS, ultraviolet-visible spectroscopy, isoelectric point, and Brunauer-Emmett-Teller techniques. The XPS results revealed the successful incorporation of Cu⁺/Cu²⁺ with different ratios. The prepared heterostructures were tested as solar active photocatalysts for Methylene Blue (MB) photodegradation. The CuO/Cu₂SnS₃ (20% Cu₂SnS₃/80% CuO) photocatalytic results exhibited a high photodegradation efficiency (90%) after 60 min. In addition, the photonic efficiency values (ζ) were calculated to be 15.9%, 44%, and 61.4% for CuO, Cu₂SnS₃, and CuO/Cu₂SnS₃ nanoheterostructures, respectively. In addition, the reactive oxidative species were detected by the trapping experiments to get a clear insight about the photocatalytic reactivity factors. Total organic carbon (TOC) was conducted to confirm the safe photodegradation of MB dye without the formation of colorless hazardous (95.5% TOC removal). Based on the electronic band structure, the mechanism of photodegradation was investigated. The currently investigated heterostructure system is narrow/narrow bandgap, which fulfills the two contradictory conditions in terms of high solar photocatalytic activity and overcomes the rapid recombination process.