Hierarchical mesoporous NiCo2O4 hollow nanocubes for supercapacitors

Abstract

In the present work, mesoporous NiCo₂O₄ hollow nanocubes are synthesized using a “coordinating etching & precipitating” (CEP) route. The hollow nanocubes are characterized using SEM, TEM, XRD, XPS and BET methods. The hollow nanocubes have a uniform morphology of 300–500 nm, a high surface area of 134.52 m² g⁻¹ and a mesoporous structure of 2.4–6 nm. These mesoporous NiCo₂O₄ hollow nanocubes exhibit the specific capacitance of 795.6 F g⁻¹ at a constant discharge current density of 1 A g⁻¹. The high specific capacitance and the stability of the NiCo₂O₄ hollow nanocube electrode are attributed to its large specific surface area and mesoporous structure. The specific capacity retention is 97.5% at a current density of 1 A g⁻¹ and 96.1% at a current density of 2 A g⁻¹ over 2000 charge–discharge cycles. The high specific capacitance and excellent cyclic stability indicate that NiCo₂O₄ hollow nanocubes are excellent supercapacitor electrode materials.