Construction of Fe3O4@Fe2P Heterostructures as Electrode Materials for Supercapacitors

Considering their high abundance in the earth, iron-based materials have occasionally been regarded as promising electrode materials for supercapacitors. However, monometallic iron-based electrodes still demonstrate an insufficient specific capacitance value in comparison to monometallic Mn-, Ni-, and Co-based compounds and their combined materials. Herein, an enhanced iron-based heterostructure of Fe3O4@Fe2P was prepared via the in situ phosphorization of Fe3O4. Compared to pristine Fe3O4, the Fe3O4@Fe2P heterostructure showed a capacity enhancement in KOH aqueous solution. The improved electrochemical performance can be attributed to both the core shell structure, which favors buffering the collapse of the electrode, and the synergistic effect between the two iron compounds, which may provide abundant interfaces and additional electrochemically active sites. Moreover, the assembled asymmetric supercapacitor device using the Fe3O4@Fe2P heterostructure as the positive electrode and activated carbon as the negative electrode delivers a high energy density of 13.47 Wh kg−1, a high power density of 424.98 W kg−1, and an acceptable capacitance retention of 78.5% after 5000 cycles. These results clarify that monometallic Fe based materials can deliver a potential practical application. In addition, the construction method for the heterostructure developed here, in which different anion species are combined, may represent a promising strategy for designing high-performance electrodes.