In situ synthesis of a non-toxic cobalt-benzimidazole metal-organic framework decorated reduced graphene oxide composite for asymmetric supercapacitor applications

In this article, we report an effective synthesis of a cobalt-benzimidazole metal organic framework (Co-Bi-m MOF), which belongs to the Zeolitic imidazolate framework-9 (ZIF-9) family, and a cobalt-benzimidazole MOF@reduced graphene oxide (Co-Bi-m@rGO) composite through hydrothermal treatment for supercapacitor application. The structural and morphological features of the Co-Bi-m MOF and Co-Bi-m@rGO composite were confirmed by using various physicochemical techniques such as FT-IR, Raman, XRD, SEM, TEM, BET and XPS analysis. The SEM and BET analysis of the Co-Bi-m@rGO composite shows a layer-like structure with abundant pores and a large surface area (543 m(2) g(-1)). The supercapacitive performance of the prepared electrodes was investigated using CV (cyclic voltammetry), GCD (Galvanostatic Charge-Discharge) and electrochemical impedance spectroscopy (EIS) analyses in aq. 1 M KOH. The as-fabricated Co-Bi-m@rGO composite showed a specific capacity of 1488 C g(-1) at 1 A g(-1) and maintained 96% of its initial capacitance after 8000 GCD cycles at 4 A g(-1). The superior capacity performance of the Co-Bi-m@rGO composite is mainly ascribed to its mesoporous nature with an improved surface area, multiple redox sites and synergistic effect between the Co-Bi-m MOF and rGO moiety. The constructed Co-Bi-m@rGO//AC device showed an energy density of 90.55 W h kg(-1) at a power density of 2396.28 W kg(-1), and the device showed a cyclic stability of 88% even after 4000 GCD cycles at 3 A g(-1). Further, biocompatibility analysis of the Co-Bi-m MOF and Co-Bi-m@rGO composite proved the non-toxic nature of the as-prepared electrode material. Thus, the effective energy storage ability of the Co-Bi-m@rGO composite confirms it as a potential candidate for supercapacitors in day-to-day applications.