Controllable defluorination of fluorinated graphene and weakening of C-F bonding under the action of nucleophilic dipolar solvent.

The effect of solvent on the chemical structure and properties of fluorinated graphene (FG) was particularly investigated in this work. It is found that the reduction of FG and the weakening of strong covalent C-F bonding take place under the action of some dipolar solvents even at room temperature. The rate of the C-F bond rupture reaction is positively influenced by the dipole moment of solvent and fluorine coverage of FG sheets. Meanwhile, defluorination of FG is controllable through the time and temperature of solvent treatment. These solvents function as the nucleophilic catalysts, promoting chemical transformation, which leads to a series of changes in the structure and properties of FG, such as a decline of fluorine concentration of about 40% and the reduction of thermal stability and band gap from 3 to 2 eV. After the treatment with dipolar solvent N-methyl-2-pyrrolidinone, FG maintained a capacity of 255 mA h g(-1) and a power density of 2986 W kg(-1) at a high discharge rate, while the pristine FG could not be discharged at all. This is called the "solvent activation" effect on the electrochemical performance of FG. The finding may draw attention to the effect of various external factors on the chemical structure and properties of FG, which is of great importance for the realization of the FG's potential.