Plasmonic ZnO/Au/g-C3N4 nanocomposites as solar light active photocatalysts for degradation of organic contaminants in wastewater

Abstract

In the present study, novel ZnO/Au/graphitic carbon nitride (g-C3N4) nanocomposites were fabricated via a facile and eco-friendly liquid phase pulsed laser process followed by calcination. Notably, the approach did not necessitate the use of any capping agents or surfactants. The as-prepared photocatalysts were evaluated by various electron microscopy and spectroscopy techniques. The obtained results confirmed good dispersion of the Au nanoparticles (NPs) on the surface of spherical ZnO particles deposited on the g-C3N4 nanosheets. The ZnO/Au/g-C3N4 nanocomposite exhibited substantially enhanced catalytic activity toward the degradation of methylene blue (MB) under simulated solar light irradiation. In particular, the ZnO/Au15/g-C3N4 composite containing 15 wt% Au displayed a rate constant, which was approximately 3 and 5 times greater than those of pristine g-C3N4 and ZnO, respectively. This improved photocatalytic activity of ZnO/Au15/g-C3N4 was attributed to the surface plasmon resonance of Au NPs and the synergistic effects between ZnO and g-C3N4. The boundary between ZnO/Au and g-C3N4 enabled direct migration of the photogenerated electrons from g-C3N4 to ZnO/Au, which hindered the recombination of electron–hole pairs and enhanced the carrier separation efficiency. Additionally, a plausible MB degradation mechanism over the ZnO/Au/g-C3N4 photocatalyst is proposed based on the results of the conducted scavenger study.