1D/2D hierarchical carbon architectures with tunable porosity for high-performance ionic liquid supercapacitors

The fabrication of carbon electrode materials with hierarchically porous structures and excellent ion/electron transport capability is crucial for supercapacitors with high energy density to date. Herein, the controllable preparation of hierarchical porous carbon architectures (denoted as PCCN) made of 1D carbon backbones and 2D carbon nanosheets is achieved by a chemical activation coupled with exfoliation-like effects of in-situ generated carbon dioxide (CO 2 ) gas from potassium bicarbonate (KHCO 3 ). It is found that the modulation of carbonization temperature and KHCO 3 dosage permits the formation of PCCN samples with tunable microstructures. The optimized PCCN 1:5-900 sample exhibits a large specific surface area of 1770 m 2  g −1 with a specific pore size distribution and interconnected porous frameworks, which can provide abundant ion-accessible electrode/electrolyte interfaces and fast ion/electron transport channels. Consequently, the assembled symmetrical PCCN 1:5-900 //PCCN 1:5-900 supercapacitor delivers a prominent specific capacitance of 144 F g −1  at 0.5 A g −1 , i.e. a high-energy density of 72.1 Wh kg −1  at an output power density of 477 W kg −1 , superior rate performance with capacitance retention of 63 % even at 100 A g −1 , and admirable cycling durability in the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4 ) ionic liquid electrolyte. This work provides a feasible and sustainable method to make advanced carbon electrodes for ionic liquid and/or organic supercapacitor systems.