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 m(2) 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.