Preparation and electrochemical performance of Ni(OH)2 nanowires/three-dimensional graphene composite materials

Abstract

We synthesized Ni(OH)2 nanowires/three-dimensional graphene composites using a hydrothermal method, and compared their properties with those of three-dimensional graphene, Ni(OH)2 nanowires, reduced graphene oxide, and Ni(OH)2 nanowires/reduced graphene oxide. The samples were characterized using Xray diffraction, scanning electron microscopy, thermogravimetric analysis, and N2 physisorption measurements. The electrochemical performances were investigated using cyclic voltammetry and galvanostatic chargedischarge methods. The results showed that Ni(OH)2 nanowires of width 20–30 nm were closely combined with graphene and crosslinked to one another to form a three-dimensional structure with a high specific surface area (136 m2∙g–1) and mesoporosity (pore diameter 20–50 nm). The mass fraction of Ni(OH)2 nanowires in the Ni(OH)2 nanowires/three-dimensional graphene composite was 88%. The maximum specific capacitance of the Ni(OH)2 nanowires/three-dimensional graphene composite was 1664 F∙g–1 in 6 mol∙L–1 KOH electrolyte at 1 A∙g–1. The specific capacitance decreased by only 7% after 3000 cycles at 1 A∙g–1. A comparative study of the specific capacitances and cycling performances of Ni(OH)2 nanowires, Ni(OH)2 nanowires/reduced graphene oxide, three-dimensional graphene, reduced graphene oxide, and Ni(OH)2 nanowires/three-dimensional graphene indicated that three-dimensional graphene with three-dimensional porosity and a larger specific surface area than conventional reduced graphene oxide enabled improved use of the active material and significantly enhanced the electrochemical performance of Ni(OH)2 nanowires.