Silver quantum cluster (Ag₉)-grafted graphitic carbon nitride nanosheets for photocatalytic hydrogen generation and dye degradation

We report the visible-light photocatalytic properties of a composite system consisting of silver quantum clusters [Ag₉(H₂MSA)₇] (H₂MSA=mercaptosuccinic acid) embedded on graphitic carbon nitride nanosheets (AgQCs-GCN). The composites were prepared through a simple chemical route; their structural, chemical, morphological, and optical properties were characterized by using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, transmission electron microscopy, UV/Vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Embedment of [Ag₉(H₂MSA)₇] on graphitic carbon nitride nanosheets (GCN) resulted in extended visible-light absorption through multiple single-electron transitions in Ag quantum clusters and an effective electronic structure for hydroxyl radical generation, which enabled increased activity in the photocatalytic degradation of methylene blue and methyl orange dye molecules compared with pristine GCN and silver nanoparticle-grafted GCN (AgNPs-GCN). Similarly, the amount of hydrogen generated by using AgQCs-GCN was 1.7 times higher than pristine GCN. However, the rate of hydrogen generated using AgQCs-GCN was slightly less than that of AgNPs-GCN because of surface hydroxyl radical formation. The plausible photocatalytic processes are discussed in detail. Silver metal quantum clusters embedded in graphitic carbon nitrides have been developed as new photocatalysts for environmental remediation and hydrogen evolution (see figure; Ag₉=nine-atom silver clusters; H₂MSA=mercaptosuccinic acid; GCN=graphitic carbon nitride nanosheets).