Co3O4 Nanocrystals on Crab Shell-derived Carbon Nanofibers (Co3O4@CSCNs) for High-performance Supercapacitors

Abstract

Waste crab shell (CS) is implemented to prepare highly N-doped and CS-derived hierarchical porous carbon nanofibers (CSCNs) capable of high-performance supercapacitors combining with Co3O4 nanocrystals. The fiber nature of the exoskeleton of CSs is transformed to N-containing organic nanofibers, which are carbonized and subsequently activated by hot CO2 treatment to control the specific surface area (SSA) and pore size distribution (PSD). The interwoven bundles of CSCNs present intrinsic macroporosity whereas mesopores (˂10 nm) are generated at the interspace between CSCNs. The CO2-activated CSCNs show an ultra-high SSA of 2430 m(2)/g, combining with N-doping levels of 2.1 wt %. In addition, highly N-doped hierarchical CSCNs are utilized as supercapacitors hybridized with Co3O4 nanocrystals (Co3O4@CSCN). The Co3O4@CSCN exhibits superior capacitances of 508 F/g at 1 A/g, outstand rate capacitances and 374 F/g (74%) even at 50 A/g, and excellent long-term cycling stability of 470 F/g (95%) at 2 A/g over 10 000 cycles. Such excellent electrochemical performance is attributed to the synergic effect of redox sites and electric double layer capacitance of highly porous CSCNs, augmented electric conductivity and wettability due to N-doping, enhanced charge transfer caused by small crystal sizes and large interfaces of CSCNs, and easy electrolyte diffusion due to the genuine hierarchy of CSCN.