Synthesis Of Fe/N Co-Doped Porous Carbon Spheres Derived From Corncob For Supercapacitors With High Performances

Corncob, as a sustainable biomass waste, is mainly composed of hemicellulose. Herein, on the basis of natural corncob as substrates, Fe/N co-doped porous carbon spheres were designed via a consecutive FeCl3-mediated hydrothermal reaction and mild KHCO3 activation route for supercapacitor electrode materials. Owing to the low hydrolysis temperature of hemicellulose and hydrolysis promotion of Fe3+, the corncob-derived hydrochar exhibited special carbon sphere morphology. Interestingly, the carbon sphere morphology was well-preserved upon the melamine-mediated KHCO3 activation. As a result of the short ion diffusion distance, unique packing architecture, and developed micro-mesoporous structure of the carbon spheres, optimized CCAC-Fe-M-50% manifested superior ion transfer kinetics and rate performances (87% up to 20 A g(-1)). Meanwhile, the electrochemical investigation of CCAC-Fe-M-50% in a three-electrode setup illustrated high capacitance (338 F g(-1) at 1 A g(-1)). In a two-electrode setup, the CCAC-Fe-M-50%parallel to CCAC-Fe-M-50% device revealed supreme cyclability (102.7% retention after 5000 cycles) and extremely low R-ct (0.59 Omega) and R-s (4.54 Omega). These superior properties were attributed to the large S-BET (2305.7 m(2) g(-1)), the multiple redox possibilities (Fe3+, Fe2+, and N functional groups), and the carbon sphere morphology with a micro-mesoporous structure, which enhanced ion physisorption, pseudocapacitance, and electrolyte/ion diffusion, respectively. Besides, the fabricated CCAC-Fe-M-50%parallel to CCAC-Fe-M-50% device in a neutral electrolyte demonstrated a superb energy density (E-D) of 18.60 Wh kg(-1) at the power density (P-D) of 455 W kg(-1). The currently presented strategy with superior results might lead to the novel development of biomass-based ultraperformance electrode materials for supercapacitors and other high-tech applications.