S-scheme mechanism in the TiO2/Cu2O@Cu system toward selective degradation of an electron-rich dye pollutant under solar light

This research aims to reach a selective nanocomposite based on Cu and TiO2 nanoparticles (NPs) through a sol-gel followed by chemical reduction. Various methods such as XRD, SEM, TEM, HRTEM, BET, Raman, FTIR, DRS, XPS and PL analysis were used to characterize the prepared NPs. The reduced nature of Cu in nanocomposite was evidenced by its X-ray photoelectron spectral characteristics and its HRTEM image. Due to the presence of Cu NPs, light absorption in solar radiation by nanocomposite was considerably enhanced and caused more efficient charge carriers separation. A CCD was used to evaluate the photoactivity of the solar-driven photocatalyst by degrading methylene blue (MB) as a single model electron-rich organic pollutant. In optimal conditions, the highest photocatalytic activity reached 95.64 %. In this study, band structure and reactive species scavenging results confirmed an S-scheme mechanism for charge carrier transfer during photodegradation. The plasmonic S-scheme TiO2/Cu2O@Cu heterojunction photocatalyst exhibited remarkably strong photocatalytic selectivity toward MB in binary mixtures of MB with eosin B and rhodamine B. A preference for degradation of MB over safranin (Saf) is confirmed by the faster degradation rate of MB than that of Saf. S-scheme mechanism, Cu doping and dye sensitization all contributed to outstanding selective photodegradation performance.