Preparation of NiCo2O4@CoS heterojunction composite as electrodes for high-performance supercapacitors.

[Display omitted] • NiCo 2 O 4 @CoS core/shell nanowire arrays on Ni foam were prepared. • The electrode exhibits a higher specific capacitance of 1902.5F g−1 at 1 A g−1. • A hybrid capacitor has an energy density of 39.7 Wh kg−1. • DFT provides assistance for the enhanced electrochemical performance. It is a preferred method by constructing core − shell structured composites with heterojunctions to enhance the charge transfer and improve electrochemical performances for supercapacitors. In this work, we prepare NiCo 2 O 4 @CoS electrode materials on nickel foam via coating n − type CoS on p − type NiCo 2 O 4 to form heterojunctions. The composite shows a synergistic effect from each component and has abundant active sites, as well as outstanding reaction kinetics. Density functional theory (DFT) analysis reveals that the NiCo 2 O 4 @CoS composite exhibits higher electronic conductivity than any single component. The NiCo 2 O 4 @CoS electrode presents an outstanding capacitance of 1902.5F g−1 at the current density of 1 A g−1. A hybrid capacitor with NiCo 2 O 4 @CoS as the positive electrode and activated carbon as the negative electrode shows a high energy density of 32.91 Wh kg−1 at the power density of 425 W kg−1 and an excellent stability of 81.5% initial capacitance after 5000 cycles at 1 A g−1. The conclusions indicate that the heterojunction of NiCo 2 O 4 @CoS can be a potential electrode for supercapacitors. [ABSTRACT FROM AUTHOR]