Rapid photocatalytic degradation of RhB dye and photocatalytic hydrogen production on novel curcumin/SnO2 nanocomposites through direct Z-scheme mechanism

Abstract

For a first time, curcumin/SnO2 nanocomposites were synthesized by combined sol–gel assisted ultrasonic route for photocatalytic degradation of RhB dye and hydrogen production. The as-synthesized novel nanoparticles were systematically characterized by XRD, N2-adsorption–desorption isotherm, DRS, PL, XPS, and HRTEM. Surprisingly, the color of the nanocomposite turned reddish yellow upon incorporation of curcumin which taken as evidence for charge transfer complex between SnO2 and curcumin. Particularly, a reduction in XRD and PL intensity reflect the strong chemical interaction between SnO2 and curcumin. The as-achieved curcumin/SnO2 nanocomposites exhibits an excellent photoreactivity and stability toward degradation of RhB dye with optimal concentration 5 wt% curcumin for removal 95% of RhB dye on 0.5 g/l photocatalyst in 120-min under visible light radiations compared with 38% removal on bare SnO2 under the same reaction conditions. The amount of hydrogen evolved reaches 15 mmol h−1 g−1 on the optimized sample compared with 3 mmol g−1 h−1 on bare single oxide. The excellent photocatalytic reactivity was attributed to the charge migration through Z-scheme mechanism in which holes and electrons in the inferior energy levels are recombine, however, those at higher energy level are maintained with strong oxidizing and reducing power. This novel Z-scheme mechanism not only enhances the oxidation and reduction efficiency of the photogenerated holes and electrons, but also, improve the quantum efficiency of electron–hole separation. This research will open a door for synthesis new nanocomposite for renewable energy source and wastewater treatment.