Facile fabrication of carbon nanosheets with hierarchically porous structure for high-performance supercapacitor

Carbon nanosheets have been considered as promising candidates for supercapacitors. However, it is still challenging to construct carbon nanosheets incorporating nanoscale thickness and controllable hierarchically porous structure. Herein, a type of novel carbon nanosheets with well-developed hierarchical micro-/meso-/macropores are synthesized by combining bubbling and templating methods, in which an organic-metal salt (ferrous gluconate) with low melting point is used as carbon source. The prepared carbon nanosheets have exceptional structural controllability, that is, the sheet thickness can be well tailored from 142 to 53 nm, and the embedded pores are adjustable in the range of 20 nm-168 nm. Meanwhile, owing to robust carbon skeleton to tolerate the KOH etching, the surface area of carbon nanosheets can be raised to 3230 m(2) g(-1) after an activation process. Based on these unique structural merits, the carbon nanosheets exhibit attractive supercapacitive performance. The specific capacitance can reach 235 F g(-1) at 0.1 A g(-1), and even at a very large current density of 50 A g(-1), a high capacitance of 168 F g(-1) is still retained, indicating good retention of 71%.