Synthesis and electrochemical evaluation of cobalt-based ZIF-67 with its potential as direct use electrode materials for supercapacitors

Zeolitic Imidazolate Frameworks containing imidazolate-based linkers were successfully prepared into three different molar ratios 3:10, 1:1, and 10:3 mmol. The effect of 2-methylimidazole (HmIM)/ Cobalt (II) nitrate hexahydrate (Co(NO3)2·6H2O) molar ratio on the physicochemical characteristics of Co-based ZIF-67 showed that Co-ZIF-R3 has achieved the highest specific capacity of 86 C g−1 at 0.25 A g−1 in 1 M KOH. An asymmetric supercapacitor (ASC) utilising Co-ZIF-R3 as fabricated cell exhibited 32 C g−1 at current density of 0.25 A g−1 within a large working potential of 1.70 V. Furthermore, 87% of its capacity was kept after 2500 cycles at the reversible current density of 0.50 A g−1 until 1.0 A g−1 revealed its high potential as electrode material for supercapacitor. This work not only amplified the information of direct use of MOF as cathode material in supercapacitors, but also the relation of the role of Co/HmIM molar ratio on the electrode materials with good electrochemical performance.