Electric‐Field‐Assisted Enhanced Electron Transfer to Boost Supercapacitor Negative Electrode Performance for a Fabricated Fe 7 S 8 /α‐FeOOH Nano‐Heterostructure

The shortcoming of Fe‐based materials, their poor electron transfer efficiency, restricts their electrochemical performance severely. An electric field ( E ) is induced by an Fe 7 S 8 /α‐FeOOH nano‐heterostructure (SACF) via two simple immersion steps at room temperature. The charge transfer from α‐FeOOH to Fe 7 S 8 spontaneously establishes an intrinsic electric field at the Fe 7 S 8 /α‐FeOOH nano‐heterostructure boundary. Additionally, the relationship between structure and property is investigated by structural characterization and density functional theory calculations that are used to explain the electron transfer mechanism and good wettability in KOH electrolyte. The results indicate that the electric field accelerates the electron transfer rate during charge/discharge process, provides the most of active materials (both Fe 7 S 8 and α‐FeOOH) and facilitates the contact of active material with electrolyte. When used as the supercapacitor negative electrode, the SACF delivers superior specific capacity of 520.27 F g −1 at 1 A g −1 current density, 2.5 times that of the ACF (α‐FeOOH nanosheet array), and shows excellent cycle life and rate capacity. This work introduces the consideration of electric field into fabricating an effective supercapacitor negative electrode, and helps to understand the function mechanism of nano‐heterojunction when designed in electrode materials.