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

Abstract 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 NiCo2O4@CoS electrode materials on nickel foam via coating n − type CoS on p − type NiCo2O4 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 NiCo2O4@CoS composite exhibits higher electronic conductivity than any single component. The NiCo2O4@CoS electrode presents an outstanding capacitance of 1902.5F g−1 at the current density of 1 A g−1. A hybrid capacitor with NiCo2O4@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 NiCo2O4@CoS can be a potential electrode for supercapacitors.