Improving charge transfer via nickel–nickel oxide/molybdenum dioxide heterostructure for advanced supercapacitor electrode

Abstract

Currently, asymmetric supercapacitors (ASCs), as significant energy storage devices, have gained tremendous attention for alleviating the ever-increasing demands of carbon-free energy. Herein, metallic nickel decorated nickel oxide/molybdenum dioxide nanorods are directly anchored on porous nickel foam (Ni-NiO/MoO2/NF) by a hydrothermal method and subsequent reduction engineering under H2/Ar aura. The H2-reduction induced oxygen vacancies, multi-phase configurations, and rich interfaces synergistically enchace the electrochemical energy storage capabilities of the Ni-NiO/MoO2/NF. Notably, the density functional theory (DFT) results indicate that the generated interfaces of both Ni/NiO and Ni/MoO2 facilitate the metallic characteristic and thus enhance the electrochemical redox activity. Consequently, the Ni-NiO/MoO2/NF shows a specific capacity of 256.8 C g–1 at 1 A g–1 and 159.9 C g–1 at 20 A g–1, as well as a good cycling durability (remains 90.7% capacity after 8000 cycles) in 2.0 M of KOH media. In addition, an ASC with a voltage window of 1.4 V is constructed by employing the Ni-NiO/MoO2/NF and activated carbon (AC) as positive electrode and negative electrode, respectively, which exhibits an energy density as 28.8 Wh kg−1 at 777.8 W kg−1 and 80.2% capacity retention after 8000 charge/discharge operation. Further, a home-made ASC is assembled and exhibits potential application to power an electric fan. This work provides an efficiently way to construct multi-component electrodes with abundant heterostructures for applications in portable devices.