Hierarchically porous carbons with graphene incorporation for efficient supercapacitors

Simultaneous improvement in capacitance, rate capability and cycleability of electrode material is highly desired for high-performance supercapacitor, which necessitates the rational design of pore texture and surface composition of electrode materials. Herein, graphene incorporated activated carbon is synthesized by pyrolysis and alkali activation of graphene oxide-egg white (EW) precursor. The 3-dimensionally intertwined graphene mat induces the coating of EW and constructs hierarchical porosity of the resultant activated carbon. Benefit from the interconnected large mesopores/macropores channels deriving from the robust and conductive graphene mat, abundant micropores/small mesopores with slightly enlarged pore width by activation treatment, as well as the essential pseudocapacitance stemming from the N, O functionalities, high electrons/ions conductivities and considerable capacitance can be ensured. As a result, dramatically enhanced overall capacitance can be offered under higher current densities and consecutive charging-discharging cycles. The sample prepared by graphene incorporation and activation treatment of EW precursor, labeled as AGEWC, delivers a specific capacitance of 291 F g (1) at 1 A g (1) in 1 M H2SO4 electrolyte, a dramatically improved rate capability (69% capacitance maintaining ratio within 0.5 similar to 15 A g (1)) and a high cycleability (90% capacitance retention after 5000 charge-discharge cycles). The present work provides a low cost while efficient strategy to comprehensively optimize the capacitive performances of activated carbon based supercapacitors. (C) 2016 Elsevier Ltd. All rights reserved.