Outstanding energy storage performance in Co[sbnd]Fe bimetallic metal-organic framework spindles via decorating with reduced graphene oxide nanosheets

Abstract

Reduced graphene oxides (rGOs; 3 and 5 wt%) decorated on CoFe bimetallic metal-organic framework (CoFe-MOF) have been synthesized by the ultrasonic-assisted solvothermal method. XRD patterns did not show any significant amendment in crystalline structure of MIL-88A and 3 % rGO@CoFe-MOF revealed better crystallinity than other samples. TEM and FESEM images clearly demonstrated that the rGO nanosheets are coated on the CoFe-MOF spindles. BET and BJH analyzes showed that the 3 % rGO@CoFe-MOF composite had the highest specific surface area (149 m2 g−1) and mean pore size (1.79 nm) compared to the other samples. The MOF and rGO decorated on MOF samples were deposited on Ni foam (NF) and their electrochemical performance as binder-free electrodes was evaluated in 3 M KOH electrolyte. The 3 % rGO@CoFe-MOF/NF electrode exhibits outstanding specific capacitance of 2069.1 F g−1 at a current density of 0.5 A g−1 and good cycling stability with 91.3 % capacitance retention at a high current density of 10 A g−1 after 5000 cycles. The assembled 3 % rGO@CoFe-MOF//activated carbon asymmetric supercapacitor device delivers a maximum energy density of 75.8 Wh kg−1 at a power density of 700 W kg−1. The results exhibit that the 3 % rGO@CoFe-MOF can be a propitious electrode material in energy storage devices.