Application of Chemical Doping and Architectural Design Principles To Fabricate Nanowire Co₂Ni₃ZnO₈ Arrays for Aqueous Asymmetric Supercapacitors

Electrode materials derived from transition metal oxides have a serious problem of low electron transfer rate, which restricts their practical application. However, chemically doped graphene transforms the chemical bonding configuration to enhance electron transfer rate and, therefore, facilitates the successful fabrication of Co₂Ni₃ZnO₈ nanowire arrays. In addition, the Co₂Ni₃ZnO₈ electrode materials, considered as Ni and Zn ions doped into Co₃O₄, have a high electron transfer rate and electrochemical response capability, because the doping increases the degree of crystal defect and reaction of Co/Ni ions with the electrolyte. Hence, the Co₂Ni₃ZnO₈ electrode exhibits a high rate property and excellent electrochemical cycle stability, as determined by electrochemical analysis of the relationship between specific capacitance, IR drop, Coulomb efficiency, and different current densities. From the results of a three-electrode system of electrochemical measurement, the Co₂Ni₃ZnO₈ electrode demonstrates a specific capacitance of 1115 F g^–1 and retains 89.9% capacitance after 2000 cycles at a current density of 4 A g^–1. The energy density of the asymmetric supercapacitor (AC//Co₂Ni₃ZnO₈) is 54.04 W h kg^–1 at the power density of 3200 W kg^–1.