Prediction of Selective Formation of Chair- and Boat-Type 'Hydrogenated Graphene via Birch Reduction

Abstract

Practical electronic device applications using graphene-based materials dictate that their band gap must be tunable. The synthesis of hydrogenated graphene has received much attention due to the desirable effect of the gap opening in the electronic band structure. In this study, we present the reaction mechanism of graphene hydrogenation, especially through Birch reduction, and its favorable hydrogenated conformations (chair- and boat-type) on Cu(111). The reduction of graphene was achieved by the graphene g-electron delocalization in the presence of a [Li(NH3)4+"-@(NH3)] ion-pair. Li+ played an indispensable role in the graphene hydrogenation reaction by facilitating thermodynamically and kinetically favorable reactions when it interacts with the alcohol. For the hydrogenation of graphene on the Cu surface, unlike the freestanding condition, the formation energy revealed that the boat-type was thermodynamically more favorable, and the transfer of unpaired electrons of nonhydrogenated carbon atoms to Cu supports the same prediction. Our findings indicate that this boat-type hydrogenated graphene can be synthesized on Cu(111) through the mechanism of Birch reduction. Also, control of graphene band gaps is achieved by the selective formation of the chair- and boat-type conformations of graphene as self-sustained or on the substrate.