Abstract:
This study examines tailoring the electrochemical properties of transition metal
oxides ZNCO, MOFs (ZIF-67) and their composite materials for hybrid supercapacitors.
The pristine ZNCO has a good specific capacitance due to multi oxidation state but has the
pulverization effect during charging-discharging of hybrid supercapacitor which limits its
application in practical use. To mitigate these challenges, ZNCO/MOFs (ZIF-67)
composite material was successfully synthesized by using wet chemistry which shows
enhanced electrochemical performance of fabricated asymmetric HSC. The developed
ZNCO@ZIF-67 was characterized by XRD, SEM, EDS, FTIR, TEM, HRTEM and XPS
to confirm the successful incorporation of the ZNCO into ZIF-67. Further the
electrochemical analysis including CV, GCD and EIS of composite material was evaluated
through electrochemical workstation. The ZNCO@ZIF-67 composite materials showed
enhanced specific capacitance of 4215.5 Fg⁻¹ at current density of 1.5 Ag-1 which is far
better than pristine ZNCO and ZIF-67 is 2500 Fg-1 and 1400 Fg-1
respectively. Over 8500
charge discharge cycles for three electrode assembly the composite material maintains
98.2% capacity retention. The asymmetric HSC device fabricated using ZNCO@ZIF-67
(ZNCO@ZIF-67/A.C) which shows the high energy density of 59 Whkg
-1 and power
density of 1.072 kWg
-1 with capacity retention of 97.3% over 10000 cycles. The better
electrochemical properties of the composite can be attributed to the, Synergistics effects of
both the components. ZNCO has high specific capacitance and excellent electrical
conductivity while ZIF-67 provides many active sites and robust frameworks for ion
transport during electrochemical performance. Further, in electrochemical impedance
spectroscopy (EIS), ZNCO@ZIF-67 composite material demonstrated less Rct values than
pristine for their higher kinetics at interface. From the results the composite material
ZNCO@ZIF-67 shows enhanced and synergistic effect between ZNCO and ZIF-67, which
is promising electrode material for next generation hybrid supercapacitor.
