Facile Fabrication of Three-Dimensional Graphene and Metal–Organic Framework Composites and Their Derivatives for Flexible All-Solid-State Supercapacitors

Abstract

A facile and general method for the large-scale preparation of various three-dimensional (3D) graphene oxide/metal–organic framework (GO/MOF) composites is developed through a simple mixing process using MOFs and graphene oxide. This preparation method is able to rapidly produce GO/MOF composite hydrogels with controllable composition in only several minutes, which is also suitable to a series of different MOFs. The obtained GO/MOF composites are severed as the precursors for the subsequent preparation of MOF-derived composite aerogels, e.g., rGO/Fe 2 O 3 and rGO/NiO/Ni composite aerogels, through freeze-dry and calcination processes. When used as a supercapacitor electrode, the rGO/Fe 2 O 3 composite shows a good rate capability with high specific capacitances of 869.2 and 289.6 F·g –1 at the current densities of 1 and 20 A·g –1, respectively, as well as a long cycle life without obvious decrease of capacitance after 5000 cycles. Moreover, the flexible all-solid-state supercapacitor device is also fabricated based on the obtained rGO/Fe 2 O 3 composite aerogel, which exhibits a high volumetric capacitance of 250 mF·cm –3 at 6.4 mA·cm –3 and a capacity retention of 96.3% after 5000 cycles at 50.4 mA·cm –3, as well as an excellent mechanical flexibility.