Electrochemical studies on Ni, Co & Ni/Co-MOFs for high-performance hybrid supercapacitors

Metal-organic framework (MOF) of Ni-MOF, Co-MOF, and Ni/Co-MOF were synthesized by a facile hydrothermal method using Trimesic acid as structure directing linker. The physico-chemical properties of the synthesized MOFs were characterized by P-XRD (powder X-ray diffraction), FT-IR (fourier transform infrared spectroscopy), SEM-EDS (scanning electron microscopy/energy-dispersive X-ray spectroscopy), HR-TEM (high-resolution transmission tlectron microscope) and BET (Brunner Emmett Teller) surface area techniques. The supercapacitance performance of these MOFs were studied by electroanalytical techniques such as cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). Amongst the MOFs investigated, Ni/Co-MOF exhibited highest specific capacitance (Cs) of 2041 F g−1 at a scan rate of 2 mV s−1 and 980 F g−1 at a current density of 2.5 A g−1. Ni/Co-MOFs delivered a maximum energy density (ED) of 55.7 W h Kg−1 at a corresponding power density (PD) of 1 K W kg−1 and maximum PD of 9.8 K W kg−1 at an ED of 41.6 W h Kg−1. An outstanding supercapacitance performance with superior columbic efficiency of 98.4% and capacitive retention of 73% after 5000 cycles marks this material as potential candidate for supercapacitors (SCs). A comparative electrochemical study of these MOFs were made in three electrode system, further electrochemical performance was corelated with their physico-chemical properties.