CdSe nanorod/TiO₂ nanoparticle heterojunctions with enhanced solar- and visible-light photocatalytic activity

CdSe nanorods (NRs) with an average length of ≈120 nm were prepared by a solvothermal process and associated to TiO₂ nanoparticles (Aeroxide^® P25) by annealing at 300 °C for 1 h. The content of CdSe NRs in CdSe/TiO₂ composites was varied from 0.5 to 5 wt %. The CdSe/TiO₂ heterostructured materials were characterized by XRD, TEM, SEM, XPS, UV-visible spectroscopy and Raman spectroscopy. TEM images and XRD patterns show that CdSe NRs with wurtzite structure are associated to TiO₂ particles. The UV-visible spectra demonstrate that the narrow bandgap of CdSe NRs serves to increase the photoresponse of CdSe/TiO₂ composites until ≈725 nm. The CdSe (2 wt %)/TiO₂ composite exhibits the highest photocatalytic activity for the degradation of rhodamine B in aqueous solution under simulated sunlight or visible light irradiation. The enhancement in photocatalytic activity likely originates from CdSe sensitization of TiO₂ and the heterojunction between these materials which facilitates electron transfer from CdSe to TiO₂. Due to its high stability (up to ten reuses without any significant loss in activity), the CdSe/TiO₂ heterostructured catalysts show high potential for real water decontamination.