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

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.