Silver-substituted cobalt zeolite imidazole framework on reduced graphene oxide nanosheets as a novel electrode for supercapacitors

Abstract

Although metal-organic frameworks demonstrate enhanced surface area, incredible porosity, and a well-controlled structure, they exhibit low conductivity, limiting their use in energy storage devices. In this work, we incorporated different mass loadings of silver, the metal with the highest conductivity in the zeolitic imidazolate framework-67 (ZIF-67) to enhance the electrochemical performance of their composites. The synthesized composites were extensively characterized using various techniques, and the electrochemical characterization of the constructed electrodes in 6 M KOH was performed using a two-electrode Swagelok cell. The results showed that the composite (ZIF-67.Agx=10/RGO) formed an efficient bimetallic structure and performs optimally with a specific capacitance (Cs) of 375 F/g at 5 mV s−1 and the smallest equivalent series resistance. The electrode material exhibited promising cycling stability over 2000 cycles reaching 97 % at 2 A g−1. Moreover, its energy density reached 46.388 Wh/kg along with a power density of 199.7 W/kg. Furthermore, it possessed the maximum specific surface area with all fabricated active material composite electrodes, reaching 1105 m2/g. The proposed composite can be used in energy storage applications and the conductivity will be further enhanced by co-doping.