Hierarchical Core–Shell Structure of ZnO Nanorod@NiO/MoO₂ Composite Nanosheet Arrays for High-Performance Supercapacitors

Abstract

A hierarchical core–shell structure of ZnO nanorod@NiO/MoO₂ composite nanosheet arrays on nickel foam substrate for high-performance supercapacitors was constructed by a two-step solution-based method involving two hydrothermal processes followed by a calcination treatment. Compared to one composed of pure NiO/MoO₂ composite nanosheets, the hierarchical core–shell structure electrode displays better pseudocapacitive behaviors in 2 M KOH, including high areal specific capacitance values of 1.18 F cm^–2 at 5 mA cm^–2 and 0.6 F cm^–2 at 30 mA cm^–2 as well as relatively good rate capability at high current densities. Furthermore, it also shows remarkable cycle stability, remaining at 91.7% of the initial value even after 4000 cycles at a current density of 10 mA cm^–2. The enhanced pseudocapacitive behaviors are mainly due to the unique hierarchical core–shell structure and the synergistic effect of combining ZnO nanorod arrays and NiO/MoO₂ composite nanosheets. This novel hierarchical core–shell structure shows promise for use in next-generation supercapacitors