Preparation of hierarchically porous carbon nanosheet composites with graphene conductive scaffolds for supercapacitors: An electrostatic-assistant fabrication strategy

Activated graphene (AG) possesses high conductivity and large specific surface area (SSA), but suffers from ultralow yield and limited packing density. Therefore, the incorporation of activated pyrolytic carbon (AC) and (activated) graphene provides an alternative solution. Here, a novel and facile method combining electrostatic-assistant carbonization and KOH activation is adopted to prepare regularly-constructed graphene/AC composites. The experimental results reveal that the optimized composite is a nanosheet-shaped carbon material with highly porous AC particles compactly and uniformly decorated on few-layered graphene conductive scaffolds. It is this unique microstructure that endows the composite with an enhanced electronic conduction network, a hierarchical porosity and a SSA value as large as 2979 m2 g−1, and all of these attributes facilitate its supercapacitor applications. Compared with the optimized AG material, the optimized graphene/AC composite delivers a much higher specific capacitance and an almost identical high-rate capability in 30 wt% kOH aqueous electrolyte. Compared with the pure AC material, the optimized graphene/AC composite displays a higher specific capacitance and superior high-rate capability in 1 M Et4NBF4/AN organic electrolyte. At the same time, the optimized graphene/AC composite presents considerable supercapacitive performances in the pure ionic liquid (IL) electrolytes with a maximum energy density of 74.4 Wh kg−1.