Electrochemical Synthesis of Graphene in Molten Salts

The solubility of a boron carbide powder in molten chloride is studied in the temperature range 793–903 К. Long-term holding of boron carbide in the salt melt is shown not to form carbon films. The content of B3+ boron ions is determined by the amount of oxygen adsorbed on the surface of the boron carbide powder. Carbon forms on the titanium surface in the B4C-containing melt under the no-current conditions. Coarse precipitates consisting of multilayered graphene and graphite also form in the melt. Defect-free two-layered graphene films with a large area of about 1000 μm2 form during electrochemical synthesis in molten alkali chlorides. Raman spectroscopy is used for analysis of carbon-phase purity. Raman peaks suggest that the structure under study belongs to the allotropic modification of carbon in the sp2-hybridized state. The numerical characteristics of well-pronounced and symmetrical first- and second-order scattering lines indicate that the carbon films formed on the surface of the titanium anode are two-layered graphene with a small number of defects. The morphology of the resulting graphene film can be carefully controlled using the deposition parameters, such as the synthesis temperature, the boron carbide additive concentration, and the anode current density. The process is highly reproducible, since it has a rather low synthesis temperature of 973 K, does not require any expensive reagents, and proceeds in one stage.