Flexible nickel cobalt metal-organic frameworks/reduced graphene oxide hybrid film for high-performance supercapacitors

Abstract

Self-standing metal-organic frameworks (MOFs) with high electrical conductivity and abundant active sites are attractive in enhancing the performance of supercapacitor. Herein, the flexible two-dimension nickel cobalt metal-organic frameworks/reduced graphene oxide hybrid films (2D/2D NiCo-MOFs/rGO) have been designed and prepared for high-performance supercapacitors electrode materials via a vacuum filtration and the followed heat-treatment. Graphene oxide (GO) nanosheets serve as the conductive network to enhance the electrical conductivity of MOFs as well as a binder to bond 2D NiCo-MOFs nanosheets into a film, while 2D NiCo-MOFs nanosheets contribute the main specific capacitance of hybrid films. The as-prepared 2D/2D NiCo-MOFs/rGO hybrid film displays a high area capacitance of 4.31 F cm−2 at 1 mA cm−2, and even maintains 1.56 F cm−2 at 30 mA cm−2. Additionally, an asymmetric supercapacitor is constructed by using 2D/2D NiCo-MOFs/rGO and activated carbon films as a positive and negative electrode, respectively. It displays a high energy density of 199.4 μWh cm−2 at a power density of 801.9 μW cm−2, and an outstanding cyclic stability. This study provides a facile method to fabricate the flexible MOFs-based films for directly using as supercapacitor electrode materials.