A novel method for preparation of graphene-containing biochar and application to supercapacitors

New carbon-based materials have drawn tremendous attention in several technological applications. Here, the synthesis of graphene-containing biochar was prepared through carbonation and activation processes, using pre-oxidized magnolia flowers. In particular, the activation method was conducted in copper foil under high pressure, which led to the high biochar yield and excellent electrical conductivity of biochar for graphene-containing hybrid. Furthermore, heteroatoms (including nitrogen and oxygen) were successfully doped into the biochar. As a result, the hybrid demonstrated excellent electrical properties, at high nitrogen (1.02 %) and oxygen levels (14.80 %). The as-prepared biochar was used to produce an all solid state symmetric superconductor with a capacitance of 261.8 F g-1 at a specific current of 0.5 A g-1 , and energy density of 6.9 Wh kg-1 at powder density of 20 kW kg-1 .The enhanced electrochemical performance was attributed to the positive effect of synergy between highly conductive graphene-containing biochar and heteroatoms doping