Photocatalytic activities of graphene quantum dots constructed from four different nitropyrenes on water redox reaction and organic pollutant degradation

Graphene quantum dots (GQDs) are nanometer-sized fragments of graphene with unique characters, which make them as new interesting application candidates in the fields of chemical, environmental and energy engineering. In this paper, the four nitropyrenes with different nitration degree, such as mononitropyrene, dinitropyrene, trinitropyrene and tetranitropyrene, were successfully synthesized and used to rationally construct corresponding graphite phase quantum dots named GQD(1), GQD(2), GQD(3) and GQD(4) in turn. Subsequently, the relationship between the structure and photocatalytic activity of different intermediates for the preparation of GQD were systematically studied. Degree of polymerization and lateral size of GQDs prepared with different intermediates significantly affected their photocatalytic performance. Through comparision of the photocatalytic water splitting reaction of four GQDs, it was found that GQD(4) had the best photocatalytic efficiency among four GQDs.