Free-standing metal–organic frameworks on electrospun core–shell graphene nanofibers for flexible hybrid supercapacitors

Abstract

The development of wearable and flexible energy storage devices depends on freestanding and flexible electrodes. For new-generation supercapacitors, rational modification of graphene is essential to the creation of flexible and freestanding carbon-based electrodes with excellent potential as energy storage facilities. Herein, a novel freestanding/flexible electrode made of porous reduced graphene oxide carbonized nanofiber (GNF) with conductive bimetallic MOFs (c-MOF@GNF) is constructed via a sequential technique that involves electrospinning and in situ c-MOF growth on it. c-MOF@GNF revealed a specific capacitance of 1820 F g⁻¹ at 1 A g⁻¹, superior rate capability, and high cycling stability (92.2% capacitance retention after 14 000 cycles) with excellent mechanical flexibility because of their high specific surface area, wettability, conductivity, and abundance of active sites. In addition, flexible asymmetric devices, composed of c-MOF@GNF as the cathode and GNF as the anode, exhibit high energy densities of 52.2 W h kg⁻¹ and 799.6 W h kg⁻¹, respectively. They also have good rate capability and long-term cycle stability with 90.6% capacitance retention after 12 000 cycles, indicating their realistic use. This work offers a different approach to high-performance graphene-decorated nanofiber freestanding electrode preparation, and the method can be used with various 2D materials to create effective electrodes for flexible supercapacitors.