Dual-basic carbonate template-assisted construction of graphene-like porous carbon nanosheets from waste biomass for enhanced supercapacitor performance

Two-dimensional carbon nanosheets with graphene-like characteristics are a type of promising electrode material for supercapacitors. Herein, graphene-like porous carbon nanosheets are constructed through a green dual-basic carbonate activation pyrolysis system, with agricultural waste corn straw powder as the precursor. The results show that the coupled basic carbonate activation template has a synergistic effect on the construction of porous carbon nanosheets. The synthesized carbon nanosheets have good graphitization and excellent wettability. The obtained carbon electrode shows a high specific capacitance of 246.2 F g−1 at a current density of 0.5 A g−1. Notably, the carbon electrode exhibits a capacitance retention rate and Coulombic efficiency of 97.7 % and ∼100 %, respectively, after 10,000 cycles at 10 A g−1. Furthermore, the assembled aqueous symmetric supercapacitor demonstrates a maximum energy density of 18.7 Wh kg−1 and a maximum power density of 24.4 kW kg−1, which still retains a capacitance retention rate of 97.5 % after long-term cycles. This work provides a novel design strategy for the preparation of porous carbon nanosheets and offers technical support for the development of biomass-derived carbon-based supercapacitors. •Graphene-like carbon nanosheets were prepared via a dual-basic carbonate template.•Deeply clarified the mechanism of dual-basic carbonate activation pyrolysis.•The carbon nanosheets electrode exhibits superior electrochemical performance.