Synthesis of Co₃O₄/NiCo₂O₄ Double‐Shelled Nanocages with Enhanced Capacitive and Oxygen Evolution Reaction Properties in Battery‐Supercapacitor Hybrid Devices

Abstract

Nanomaterials with hollow shell structure were studied and used in environment and energy technology due to their high specific capacity and good cycling stability. In this study, Co3O4/NiCo2O4 double‐shelled nanocages (DSNCs) were synthesized. Firstly, ZIF‐67 (Zeolitic imidazolate framework) was synthesized at room temperature; then, a ZIF‐67/Ni−Co layered double shelled hydroxides (LDH) structure was synthesized by preparing the shell structure with the use of nickel nitrate. Finally, this LDH was calcinated at 350 °C to form Co3O4/NiCo2O4 DSNCs. Among the prepared electrodes, Co3O4/NiCo2O4‐2 DSNCs exhibited the largest specific capacity (236.18 C g−1), with high cycling stability (103.43 %, 5000 cycles). Meanwhile, the assembled Co3O4/NiCo2O4‐2//AC BSH device showed outstanding cycling stability, with a specific capacitance retention rate of 85.39 % and a good coulombic efficiency of 96.35 % even after 10000 cycles. Moreover, in oxygen evolution reaction (OER), Co3O4/NiCo2O4‐2 DSNCs also had a low Tafel slope and overpotential (158 mV). Co3O4/NiCo2O4 DSNCs with enhanced electrochemical performance demonstrate that the property of energy conversion and storage can be improved by preparation of hollow structure.