Porous ZnCo2O4 nanoparticles derived from a new mixed-metal organic framework for supercapacitors

Abstract

Cobalt-based oxides have been shown to be promising materials for application in high-energy-density Li-ion batteries and supercapacitors. In this paper, we report a new and simple strategy for the synthesis of a mixed-metal spinel phase (ZnCo₂O₄) from a zinc and cobalt mixed-metal organic framework (JUC-155). It is important to rationally design a MOF with a precise ratio (Co/Zn) and a synthetic process that is simple and time saving. After solid-state annealing of the mixed-metal MOF precursor at 400 °C for two hours, a pure ZnCo₂O₄ phase with a high surface area (55 cm² g⁻¹) was obtained. When used as electrode materials for supercapacitors, an exceptionally high specific capacitance of 451 F g⁻¹ was obtained at the scan rate of 5 mV s⁻¹. The capacitance loss after 1500 cycles was only 2.1% at a current density of 2 A g⁻¹, indicating that this phase has an excellent cycling stability. These remarkable electrochemical performances suggest that this phase is potentially promising for application as an efficient electrode in electrochemical capacitors.