Fabrication of Hierarchical Porous Carbon Nanoflakes for High-Performance Supercapacitors

In the current work, the carbon nanoflakes (CNs-Fe/KOH) and porous carbon (PC-Ni/KOH) have been produced by using Fe(NO3)3/KOH and Ni(NO3)2/KOH as the cographitization/activation catalysts to treat the natural plane tree fluff, respectively. The as-prepared carbon materials show different morphologies when treated with different metal ions. Compared with PC-Ni/KOH, the CNs-Fe/KOH have both high graphitization degree (IG/ID = 1.53) and large SBET (1416 m2/g). In a three-electrode setup, the CNs-Fe/KOH electrode shows a high specific capacitance of 253 F/g at 10 A/g, with a capacitance retention of 92.64% after 10000 cycles in 2 M H2SO4 aqueous solution, which is far better than the sample without Fe3+ addition. In 1 M LiPF6 in ethylene carbonate/diethyl carbonate organic solution, CNs-Fe/KOH-based symmetric supercapacitor also presents an excellent specific capacitance of 32.2 F/g at 1 A/g. In addition, an energy density of 39.98 W h/kg can be achieved at the power density of 1.49 kW/kg. Influence of metal ions on the morphology and structure as well as electrochemical performance of the carbon materials are further analyzed in detail. The current work provides a novel path for design and fabrication of supercapacitor electrode materials with promising electrochemical performances.