A bottom-up fabrication for sulphur (S), nitrogen (N) co-doped two-dimensional microporous carbon nanosheets for high-performance supercapacitors and H2, CO2 storage

The synthesis of two-dimensional (2D) carbon sheets with sub-nanometer pore-rich microporous morphology and an understanding of the structure-performance relationship are important to develop an advanced device for supercapacitors and gas adsorption. 2D microporous carbon nanosheets with nanometer thickness allow easy mass/ion transport and overcome the problem faced by traditional porous materials. We report a bottom-up method to form 2D S, N-doped microporous carbon nanosheets from simple organic molecules for supercapacitor and gas adsorption applications. The optimized microporous carbon nanosheets prepared at 800 degrees C (p-CNS-800) possess an average-micropore size of similar to 2.2 nm with plenty of sub-nanometer micropores (>1 nm) and provide a high surface area (2847.8 m(2) g(-1)) and pore volume (1.32 cm(-1)). These unique 2D microporous carbon nanosheets and optimal S, N doping allow easy ion diffusion, electron transport, and ion/gas storage. p-CNS-800 showed an ultra-high specific capacitance of 935 F g(-1) and 615 F g(-1) at 0.5 A g(-1) in 1 M H2SO4 and 6 M KOH, respectively. The symmetric (p-CNS-800//p-CNS-800) device delivers specific capacitances of 297.4 F g(-1) (H2SO4) and 296.12 F g(-1) (KOH) and 247.2 F g(-1) (Na2SO4) with excellent cycling stability. The symmetric device delivers an excellent energy density of 31.01 W h kg(-1) and a power density of 1720.36 W kg(-1). Moreover, S, N-doped 2D-nanosheets showed excellent H-2 and CO2 uptake. The H-2 uptake of 2D microporous carbon sheets is 2.6 wt% at 77 K under 1 bar pressure whereas CO2 uptakes are 5.5 mmol g(-1) and 2.75 mmol g(-1) at 273 and 298 K with selectivity for CO2/N-2 and CO2/CH4 being 21.8 and 2.6 respectively.

Automated summary

The synthesis of 2D carbon nanosheets with sub-nanometer pore-rich microporous morphology and the understanding of their structure-performance relationship are crucial in the development of advanced supercapacitors and gas adsorption devices.