Co₃O₄ Nanorod Decorated Cu-ZnO Nanoframe to Construct Hollow Core-Shell Structure for High Performance Asymmetric...

Core-shell structures have attracted widespread attention in supercapacitors due to their ability to achieve synergistic effects between heterogeneous components and provide abundant active sites. However, the traditional solid-core structure restricts internal ion transport pathways, leading to structural degradation and sluggish reaction kinetics during long-term charge-discharge cycles. Here, a novel hollow core-shell structure composite construction strategy was presented by growing Co₃O₄ nanorods on the surface of Cu-containing ZIF-8 precursor derived hollow Cu-ZnO nanoframe via anisotropic chemical etching and in situ metal oxidation processes (Co₃/Cu-ZnO). The hollow core effectively shortens the ion diffusion path and provides sufficient internal space to accommodate volume variation, while the Co₃O₄ nanorod shell contributes high pseudocapacitive activity through the redox reactions of its multivalent cobalt ions (Co²⁺/Co³⁺ and Co³⁺/Co⁴⁺). This hierarchical Co₃O₄ nanorod-decorated hollow nanoframe provides an enlarged accessible surface area, abundant redox-active sites, shortened ion-diffusion pathways, and sufficient internal space for maintaining structural integrity during prolonged electrochemical cycling. Consequently, the Co₃/Cu-ZnO electrode exhibits a high specific capacitance of 1177 F g^-1 at a current density of 0.5 A g^-1, which far exceeds similar metal oxide-based materials. Furthermore, the assembled asymmetric supercapacitor Co₃/Cu-ZnO//AC displays a wide operating voltage window (1.5 V), high energy density (50.21 Wh kg^-1/750 W kg^-1), and a long cycle life (retaining 94.9% capacity after 10,000 cycles). This work provides a scalable strategy to rational design metal-organic framework-derived hollow core-shell structural electrode material for high-performance asymmetric supercapacitors.