Supercapacitors Based on Mixed Nickel/Cobalt 2D MOF Coordination Nanosheets for Energy Storage

Three flexible coordination nanosheets, CoNi-nanosheet, Co-nanosheet, and Ni-nanosheet, were successfully synthesized using the liquid-liquid interfacial coordination method by the reaction of the ligand, 1,1,2,2-tetrakis(4-(2,2 ':6 ',2 ''-terpyridyl)phenyl)ethylene with nickel(II) and cobalt(II) nitrates. The effective coordination between the ligand and metal ions is confirmed using characterization techniques including Fourier transform infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. The bimetallic nanosheet, CoNi-nanosheet, demonstrates an exceptional specific capacity of 112.0 mA h g(-1) at 1 A g(-1). Furthermore, the CoNi-nanosheet maintains a capacity retention of 70.07% at 5 A g(-1) after 1000 cycles. Upon integration into an asymmetric supercapacitor configuration, the CoNi-nanosheet assembly attains a heightened energy density of 89.0 W h kg(-1) at a power density of 800 W kg(-1). Impressively, the asymmetric supercapacitor has great stability. The excellent electrochemical performance of the bimetallic CoNi-nanosheet is likely attributed to alterations of electron densities around Co2+ and Ni2+ ions.