Novel mixed nickel/cobalt hexacyanoferrate microcubes with synergistic effect for aqueous hybrid supercapacitors

Abstract

Combination of different metals in coordination compounds is an efficient strategy to improve their various properties. Herein, mixed nickel cobalt hexacyanoferrates (NixCoyHCF) microcubes of varying x:y molar ratios are synthesized by co-precipitation route and comprehensively characterized to study their material and electrochemical properties. NixCoyHCF microcubes display battery-type electrochemical energy storage mechanism in aqueous electrolytes. Among the samples, Ni1Co2HCF microcubes deliver the highest specific capacity of 134 mAh g-1 (1068 F g-1) at a current of 1 A g-1. This significant enhancement in the capacity indicates the synergistic and cooperative effects between Ni and Co sites in Ni1Co2HCF microcubes. The asymmetric supercapacitor device assembled with Ni1Co2HCF microcubes deliver an excellent energy density of 74.4 μWh cm-2 at a power density of 750 μW cm-2 and retain 87.7% of its initial capacity after 2000 cycles at a current of 5 mA cm-2, indicating its robust structural integrity and electrochemical durability. This study highlights the promising potential of mixed metal hexacyanoferrate as high-performance electrodes for aqueous supercapacitors.