Co-precipitation synthesis of nickel cobalt hexacyanoferrate for binder-free high-performance supercapacitor electrodes

Prussian blue analogue with a typical metal-organic framework has been widely used as an electrode material in supercapacitor. In this work, nickel cobalt hexacyanoferrate (Ni2CoHCF) was grown on nickel foam directly using a simple co-precipitation method. The as-prepared Ni2CoHCF was tested by transmission electron microscope, scanning electron microscope, X-ray diffraction and X-ray electron energy spectrum. The results showed that Ni2CoHCF has a unique open face-centered cubic structure. The Ni2CoHCF was used to set an asymmetric supercapacitor directly. A series of electrochemical tests showed that Ni2CoHCF had an excellent electrochemical performance. The specific capacitance of the supercapacitor was 585 C g(-1) (1300.0 F g(-1), 162.5 mAh g(-1)) at the current density of 0.5 A g(-1). After 2000 cycles, it still maintained 85.57% of its initial specific capacitance at the current density of 10 A g(-1). The energy density was 30.59 Wh kg(-1) at the power density of 378.7 W kg(-1). The results show that the supercapacitor constructed by Ni2CoHCF as an electrode material has high-current charge-discharge capacity, high energy density and long cycle life. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.