Low-temperature rapid synthesis of high-quality pristine or boron-doped graphene via Wurtz-type reductive coupling reaction

High-quality graphene nanosheets are prepared via a rapid Wurtz-type reductive coupling (WRC) reaction without the assistance of any transition metal catalysts. This method involves a nearly stoichiometric reaction of tetrachloromethane (CCl(4)) and potassium (K) at 150-210 degrees C for as short as 10 min, which possesses great advantages compared with the solvothermal method. The layer number of the as-prepared graphene is mainly less than five. The formation mechanism of graphene is proposed, which comprises of three steps, stripping off the chlorines from CCl(4) by the highly reductive K, the coupling and assembly of -C=C-and the layer growth of hexagonal carbon clusters to form graphene. Many important factors determining the quality of graphene, such as the residual chlorines, the reaction temperature and the reductant, are discussed in detail. The low residual chlorine in the reaction favors the improvement of the graphene quality. Furthermore, controllable boron doping can be easily realized by adding an appropriate amount of BBr(3). The developed method provides a cost-effective route to prepare high-quality pristine or doped graphene for mass production.