Visible-light-driven photocatalysis with Z-scheme Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions

The fabrication and improved performance of Z-scheme visible-light-driven Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have been described in this study. Fern-like silver orthophosphate (Ag3PO4) microstructures have been modified using nitrogen-doped graphene quantum dots (N-GQDs) and then have been coated by ultrathin graphitic carbon nitride (g-C3N4) sheets via a combined technique including freeze-drying and refluxing methods. Photocatalytic studies have been conducted through visible-light photo-degradation of standard methylene blue dye in aqueous media. The Ag3PO4@N-GQDs@g-C3N4 ternary nano/hetero-junctions have exhibited the promoted photocatalytic efficiency of 97.91%, which is about 1.07 and 1.34 times higher than that of Ag3PO4@g-C3N4 binary nano/hetero-junctions (91.46%) and pristine-Ag3PO4 microstructures (85.91%), respectively. The excellent recyclability of the Ag3PO4@N-GQDs@g-C3N4 photo-catalyst has been verified in the cycle operations in which the recycling efficiency could have been maintained at 94.92% after five runs of experiments. The quenching effects of scavengers have suggested that the superoxide radicals (O-2(-center dot)) and holes (h(+)) are the predominant active species governing the photocatalytic reaction of the Ag3PO4@N-GQDs@g-C3N4 ternary composite due to a Z-scheme junction. The improved photocatalytic activity of Ag3PO4@N-GQDs@g-C3N4 nano/hetero-junctions could have been ascribed to the higher visible-light harvesting capacity, better charge carrier separation and stronger oxidation and reduction ability relevant to the indirect Z-scheme system where N-GQDs act as an efficient electron transfer media.