Morphology-dependent electrochemical properties of cobalt-based metal organic frameworks for supercapacitor electrode materials

The formation of cobalt metal organic frameworks (Co-MOFs) in different solvents and mixture is studied systematically through solvothermal method. The synthesized Co-MOFs are characterized with X-ray diffraction, Field emission scanning electron microscope and Brunauer-Emmett-Teller surface analyzer to know about its crystal nature, morphology and porosity, respectively. Based on the obtained results, a possible formation mechanism of Co-MOFs has been described with respect to nucleation rate and pH. The electrochemical properties of as prepared Co-MOFs are studied in 3 M KOH for electrode material of supercapacitors. A maximum specific capacitance of 958.1 F g−1 is achieved for Co-MOF/D-E (Co-MOF synthesized in DMF/Ethanol) at a current density of 2 A g−1. Simultaneously, the capacitance retention is maintained as high as 92.3%, even after 3000 cycles. The present study demonstrates that synthesis of Co-MOF with large surface area and micropore volume could be possible using DMF/EtOH mixture solvent. The hybrid structure of nanoneedles with sharp edge nanorods offer more active sites for electrochemical reaction and ensure a higher charge storage capacity than other synthesized Co-MOFs in this work.