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Exploring anode materials with an excellent electrochemical performance is of great significance for supercapacitor applications. In this work, a N-doped-carbon-nanofiber (NCNF)-supported Fe3C/Fe2O3 nanoparticle (NCFCO) composite was synthesized via the facile carbonizing and subsequent annealing of electrospinning nanofibers containing an Fe source. In the hybrid structure, the porous carbon nanofibers used as a substrate could provide fast electron and ion transport for the Faradic reactions of Fe3C/Fe2O3 during charge–discharge cycling. The as-obtained NCFCO yields a high specific capacitance of 590.1 F g−1 at 2 A g−1, superior to that of NCNF-supported Fe3C nanoparticles (NCFC, 261.7 F g−1), and NCNFs/Fe2O3 (NCFO, 398.3 F g−1). The asymmetric supercapacitor, which was assembled using the NCFCO anode and activated carbon cathode, delivered a large energy density of 14.2 Wh kg−1 at 800 W kg−1. Additionally, it demonstrated an impressive capacitance retention of 96.7%, even after 10,000 cycles. The superior electrochemical performance can be ascribed to the synergistic contributions of NCNF and Fe3C/Fe2O3. [ABSTRACT FROM AUTHOR]

The use of renewable and environmentally friendly biomass to prepare carbon materials with a hierarchical porous structure and large specific surface area has attracted great attention in energy storage devices (Supercapacitors, SCs). Here, a succulent-leaf-derived carbon material with a hierarchical porous structure (N-S-HPC) was prepared through a one-step carbonization strategy using Mg(NO 3) 2 ·6H 2 O and ZnCl 2 as double activation agents and CH 4 N 2 S as S and N source. The N-S-HPC specific capacitance reached 455.3 F g−1 at 1 A g−1, and with 1 M Na 2 SO 4 electrolyte. The assembled N-S-HPC//N-S-HPC symmetric SCs could enhance the voltage window to 1.8 V. Meanwhile, N-S-HPC exhibited the specific energy of 19.89 Wh kg−1 (450 W kg−1) and highly stable cycling performance. Compared with previously reported biomass-derived carbon materials, N-S-HPC has the advantages of i) hierarchical porous sturcture and 2136.2 m2 g−1 maximal specific surface area, allowing accommodation of more ions; ii) 1177.5 m2 g−1 specific surface area for mesopores and macropores, providing shorter diffusion pathways; iii) rich co-doping of N (9.5 at. %) and S (2.21 at. %), increasing pseudocapacitive contribution and improving surface wettability. All these data indictae the great potential application prospect of N-S-HPC, suggesting the importance of biomass-derived carbon materials for symmetric SCs. [Display omitted] • N-S-HPC derived succulent plant leaves was prepared by a dual-activating agents (ZnCl 2 and Mg(NO 3) 2 ·6H 2 O) approach. • N-S-HPC displays an ultra-high specific capacitance, due to its a large specific surface area and rich N/S co-doping. • N-S-HPC exhibit an excellent supercapacitive properties and excellent cycling stability. [ABSTRACT FROM AUTHOR]