Tandem chemical modification/mechanical exfoliation of graphite: Scalable synthesis of high-quality, surface-functionalized graphene

Abstract

Scalable and sustainable preparation of graphene is urgently needed to address its increasing demands in basic research and practical applications. Here, we present a simple preparation of surface-functionalized graphene by ball milling graphite in the presence of an aryl diazonium salt. The efficient exfoliation of graphite is achieved through the tandem surface reaction of graphite with aryl diazonium salt and mechanical shear by ball milling. Moreover, the surface functionalities of the resultant graphene platelets are readily tuned using various aryl diazonium salts, which also provide routes for the further modification of the graphene platelets. More importantly, with 93% of the graphene platelets having layers less than 5, they contain a low quantity of structural defects (ID/IG ratio = 0.30) and a low oxygen content (10.1 atom%). Such features not only facilitate the restoration of the π-conjugated structure of graphene by thermal reduction, with the ID/IG ratio reduced to 0.11 comparable to the value of graphite, but also enhance the structural stability of the graphene platelets at low temperature. This method is ideal for scaling up, since the techniques used are industrially compatible, the chemicals employed are commercially available, and no highly polluting wastes are produced in the synthesis.