Composites of Graphene Quantum Dots and Reduced Graphene Oxide as Catalysts for Nitroarene Reduction.

Composites of graphene quantum dots (GQDs) and reduced graphene oxide (rGO) with unique three-dimensional (3D) structure are prepared and their catalytic activities for reduction of nitroarenes are explored. We demonstrate that the 3D GQDs/rGO composites are more active in nitroarene reduction than GQDs and rGO. Some of them are even more active than the Ag-embedded calcium alginate (Ag/CA) or Au-embedded calcium alginate (Au/CA) catalysts. Interestingly, their catalytic property is closely related to the ratio of GQDs to rGO in the 3D GQDs/rGO composites and GQDs-to-rGO mass ratio of 1/4 exhibits the highest catalytic activity. Raman spectra of the composites show that GQDs-to-rGO ratio is related to the number of the surface/edge defects, indicating that the sites of defect and edges are active sites. In addition, the catalytic performance of the 3D GQDs/rGO composites is also contributed by their unique 3D network structures that are beneficial for the reactant adsorption and product diffusion. Given also the long cycling duration and the easy recovery from the reaction system, 3D GQDs/rGO composites are potential applicable metal-free catalytic system for nitorarene reduction.