High performance hybrid supercapacitor based on electrochemical deposed of nickel hydroxide on zinc oxide supported by graphite electrode

Herein, a binder-free nickel hydroxide electrode was developed and improved with a thin layer of zinc oxide for a high performance supercapacitor electrode. The elaboration procedure was conducted on graphite substrate using a two-step process. Zinc oxide layer was electrodeposited on graphite to form Gr/ZnO which acted as supporting electrode for the electrodeposition of nickel hydroxide. The elaborated electrode was characterized by interferometric microscope, SEM, FT-IR, XRD and XPS. A comparison study was performed between Gr/ZnO, Gr/Ni(OH)2 and Gr/ZnO/Ni(OH)2 reveals a good synergetic effect of ZnO/Ni(OH)2 on the energy storage performance. The electrochemical properties of Gr/ZnO/Ni(OH)2 electrode were optimized at different concentrations of KOH electrolyte using CV, GCD and EIS in order to obtain the best performance. Under optimum conditions, the Gr/ZnO/Ni(OH)2 electrode reached a highest areal specific capacitance of 545.5 mF.cm−2 in 4 M KOH at current density of 1 mA.cm−2 and an excellent cycling stability where it lost only 7.3% of its original capacitance after 10,000 cycles. Furthermore, Gr/ZnO/Ni(OH)2 // AC hybrid supercapacitor deliver a high areal energy density of 65.1 μWh.cm−2 at a power density of 0.75 mW.cm−2. This study reveals that the Gr/ZnO/Ni(OH)2 modified electrode have a great interest as high performance ultra-stable supercapacitor electrode.