Rational design of nickel-cobalt selenides derived from multivariate bimetal metal-organic frameworks for high-performance asymmetric supercapacitor

Abstract

The transition metal selenides have aroused wide concern due to their potential characteristics in the energy storage and conversion. The formation of multivariate MOFs attracts much research attention and provides the essential guarantee for multivariate mixed-metal selenides. Herein, a series of isostructural MOF-74 materials with different divalent metals were prepared by changing the molar ratios of nickel to cobalt. After selenizing, CoSe2, NiSe2 and three kinds of mixed-metal selenides were easily obtained, prompting us to systematically research the effect of different metal species and molar ratios on the electrochemical performance of the mixed-metal selenides. It is found that mixed-metal selenides derived from MOF-74 display much better performance than single metal selenides, and NiCoSe-4 with a Ni/Co molar ratio of 4:1 demonstrates a high specific capacity of 211 mAh g−1 at a current density of 1 A g−1. What's more, the assembled asymmetric supercapacitor NiCoSe-4//AC shows a high energy density of 61.24 Wh kg−1 at power density of 800 W kg−1, which suggests that NiCoSe-4 as a promising electrode material possesses further research value and potential for practical applications in energy storage fields.