Two-dimensional hierarchically porous carbon nanosheets for flexible aqueous supercapacitors with high volumetric capacitance.

Two-dimensional carbon nanomaterials can be assembled into a dense film and used for flexible supercapacitors, but the high packing density leads to restacking problems and poor volumetric capacitance. To address this challenge, we report two-dimensional hierarchically porous carbon (2D-HPC) consisting of micro-, meso-, and macro-pores on the 2D sheet, which shows superior capacitance and rate capability compared with a 2D carbon nanosheet consisting predominantly of micro-pores. A flexible supercapacitor fabricated with the 2D-HPC presents a high volumetric capacitance of 412 F cm-3, a high volumetric energy density of 9.2 mW h cm-3 and a power density of 120 mW cm-3.