Metal–Organic Framework Templated 3D Hierarchical ZnCo₂O₄@Ni(OH)₂ Core–Shell Nanosheet Arrays for High‐Performance Supercapacitors

Abstract

Abstract Designing core–shell electrode materials with desired components and architectures is a promising strategy for boosting electrochemical performance. Here, three‐dimensional hierarchical ZnCo 2 O 4 @Ni(OH) 2 core–shell nanosheet arrays have been successfully fabricated on a Ni foam substrate, in which the porous ZnCo 2 O 4 nanosheet “core” as the conductive scaffold was synthesized by a metal–organic framework (MOF)‐templated method, and the ultrathin Ni(OH) 2 nanoflakes “shell” with rich active sites were grafted on the ZnCo 2 O 4 nanosheet through a hydrothermal treatment. When directly used as a free‐standing electrode for supercapacitor, these hierarchical ZnCo 2 O 4 @Ni(OH) 2 core–shell nanosheet arrays exhibited a high capacitance of 3063.2 mF cm −2 (1021.1 F g −1 ) at the current density of 1 mA cm −2 . This electrode significantly outperformed individual Ni(OH) 2 or ZnCo 2 O 4 nanosheet arrays, benefiting from the robust core–shell arrays on Ni foam with good electrical conductivity and abundant active sites, as well as the synergetic effect between MOF‐derived porous ZnCo 2 O 4 “core” and the ultrathin Ni(OH) 2 “shell”. Moreover, the assembled ZnCo 2 O 4 @Ni(OH) 2 //activated‐carbon asymmetric supercapacitor displayed excellent energy and power densities (maximum of 40.0 Wh kg −1 and 8.02 kW kg −1 ) and superior cycling stability of 98.4 % retention with 91.2 % coulombic efficiency over 5 000 cycles at 10 A g −1 .