Construction of nitrogen-doped porous carbon buildings using interconnected ultra-small carbon nanosheets for ultra-high rate supercapacitors

Here, for the first time, we demonstrate a facile one-step construction of a nitrogen-doped porous carbon building (N-PCB) using interconnected ultra-small carbon nanosheets through the carbonization of biomass (Auricularia) using ZnCl2 as the activating agent and NH4Cl as the nitrogen source. Due to its high specific surface area (1607 m(2) g(-1)) with a high mesopore ratio (91%), interconnected porous structure with short ion diffusion paths, and nitrogen doping (4.8 at%), the N-PCB electrode exhibits a high specific capacitance of 347 F g(-1) at 1 A g(-1), excellent rate capability (278 F g(-1) at 50 A g(-1), 80% of capacitance retention) and outstanding cycling stability (only 2% loss in specific capacitance after 10 000 cycles). Moreover, the assembled N-PCB symmetric supercapacitor is stabilized with excellence cycling stability (4% loss after 20 000 cycles) at 1.6 V in 1 M Na2SO4 aqueous electrolyte, delivering a high energy density of 22 W h kg(-1), much higher than that of most of the reported carbon-based symmetric supercapacitors in aqueous electrolytes. Therefore, these exciting results suggest a low-cost and environmentally friendly design of electrode materials for high-performance supercapacitors.