Hierarchical mesoporous NiCo₂O₄ hollow nanocubes for supercapacitors

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.