Homogeneous Fluorine Distribution in Graphene through Thermal Dissociation of Molecular F2: Implications for Thermal Conduction and Electrical Insulation

Abstract

Direct fluorination utilizing F2/N2 was confirmed to be one of the most efficient approaches to decorate graphene. The conventional opinion holds the view that direct fluorination is a molecular fluorination process, which often makes for the preparation of fluorinated graphene (FG) with heterogenous fluorine distribution. Herein, a fluorination strategy with an atomic fluorination mechanism was developed to modify graphene through thermal predissociation of molecular fluorine into atomic fluorine. By means of theoretical simulation, the thermal dissociation process of F2 was disclosed, and dissociation temperature was determined to be about 140–180 °C. Consequently, an ingenious thermal annealing at 180 °C was employed to splitting F2 into fluorine atoms before the fluorination reaction. Distinguished from the traditional molecular fluorination, atomic fluorination using fluorine atoms enables the preparation of FG with a higher fluorination degree and relatively homogeneous fluorine distribution because of the zero-energy barrier reaction, which was validated by aberration-corrected transmission electron microscopy directly. Furthermore, FG with homogeneous fluorine distribution possesses several advantages over the heterogenous fluorine distribution samples including higher thermal stability, higher thermal conductivity, and better electrical insulation, thereby demonstrating the possibility of their application in the field of thermal conduction and electrical insulation for microelectronics. We believe that this unique fluorination approach and corresponding mechanism can be extended to other carbon materials.