Mechanochemical Preparation of Edge-Selectively justify Hydroxylated Graphene Nanosheets Using Persulfate via a Sulfate Radical-Mediated Process

Graphical Grind and sonicate : A green mechanochemical process is developed to prepare edge-selectively hydroxylated graphene (EHG) nanosheets. As-prepared EHG nanosheets have abundant OH groups at the edges and low defects in the basal planes, yielding good dispersibility in water, high near-IR photothermal conversion efficiency at 1064 nm, and excellent electrochemical performance. The production of water-dispersed graphene with low defects remains a challenge. The dry ball milling of graphite with additives produces edge-selectively functionalized graphene. However, the “inert” additives require a long milling time and cause inevitable in-plane defects. Here, the mechanochemical reaction of graphite with persulfate solved the above drawback and produced edge-selectively hydroxylated graphene (EHG) nanosheets through a 2 h ball-milling and a subsequent 0.5 h sonication. The mechanochemical cleavage of persulfate yielded SO 4 ⋅ − to spontaneously oxidize graphite to form the carbon radical cations selectively at edges, followed by hydroxylation with water of moisture. Because the O−O bond dissociation energy of persulfate is 20 % of the graphitic C−C bond, the rather low milling energy allowed the hydroxylation of graphite at edges with nearly no in-plane defects. The obtained EHG showed high water-dispersibility and excellent photothermal and electrochemical properties, thereby opening up a new door to fabricate graphene-based composites.