In-situ activation endows the integrated Fe3C/Fe@ nitrogen-doped carbon hybrids with enhanced pseudocapacitance for electrochemical energy storage

Limited energy density of carbon material stimulates the further development of other advanced negative electrodes for supercapacitors. Herein, a facile strategy is presented for the fabrication of nitrogen-doped carbon matrix encapsulated with the Fe3C/Fe nanoparticles core-shell architectures. The obtained hybrid is constructed by interwoven carbon nanosheets, pod-like carbon nanotubes and Fe3C/Fe nanoparticles, yielding integrated porous conductive networks. Interestingly, after fifteen cyclic voltammetry cycles, the Fe3C/Fe@NC as negative electrode exhibits a much enhanced pseudocapacitance of 1695 F g(-1) at 2 A g(-1). The in-depth analyses indicate that a dominant Fe3O4 phase with new morphology is formed during the electrochemical activation processes. Thus, the authentic active species accounted for the Faradaic redox reactions should be the Fe3O4, rather than the Fe3C/Fe itself. Furthermore, the assembled asymmetric supercapacitor with Fe3C/Fe@NC as the anode and Ni(OH)(2) as the cathode delivers a high energy density of 72 Wh kg(-1) at a power density of 0.83 kW kg(-1) and a long cycling life, which is superior to those of other reported iron-based materials. This work not only provides a simple in situ activation approach to realize the utilization of Fe3C/Fe, but also paves an avenue for developing advanced negative materials for supercapacitors.