Metal–Organic Framework-Derived Hierarchically Heterostructured ZnCo₂O₄/ZnO Composites for High-Performance Supercapacitors

Three-dimensional hierarchically structured ZnCo₂O₄/ZnO (ZnCoO) composites have been prepared through a simple thermal treatment of ZnCo-bimetal MOF (ZnCo-MOF) precursors. We found that the solvothermal reaction temperature for preparing ZnCo-MOFs has an important influence on the composition and structure of the ZnCoO composites. When the temperature is 100 °C, ZnCoO-100 and ZnCoO-100-P (PVP added) present well-defined hierarchical cubic structures composed of loosely packed nanoplates and nanorods, in which ZnO is the major component. When the temperature is increased to 150 °C, ZnCoO-150 and ZnCoO-150-P show hierarchically coral-like structures consisting of interconnected nanoparticles with ZnCo₂O₄ as the main phase. As electrode materials of supercapacitors, ZnCoO-150-P exhibits the most outstanding electrochemical performance, achieving 1266 F g^-1 at 1 A g^-1 with 85.3% retention at 20 A g^-1 and preserving 91.6% of its initial capacitance after 10 000 cycles, which stems from the synergistic optimization of its composition and structure. In addition, the assembled asymmetric supercapacitor device (ZnCoO-150-P//AC) can deliver 78.3 Wh kg^-1 at 750 W kg^-1 and retain 90.1% of its initial capacitance over 10 000 cycles, revealing its practical application potential.