A 3D hierarchical porous α-Ni(OH)2/graphite nanosheet composite as an electrode material for supercapacitors

Abstract

Supercapacitors are the most promising energy storage devices by virtue of high power density, long cycle life, short charging time and environmental benignity. In order to enhance the energy density, rate capability and cycle stability for supercapacitors, a α-Ni(OH)2/graphite nanosheet composite is prepared via a homogeneous precipitation method. The morphology and microstructure of the as-prepared composite are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. It is demonstrated that after introducing the graphene oxide nanosheets into α-Ni(OH)2, a 3D hierarchical porous structure of fine α-Ni(OH)2 nanocrystals as building blocks is formed directly on the matrix of graphite nanosheets in the presence of urea as a mild reducing agent. The electrochemical performance of the as-prepared α-Ni(OH)2 and α-Ni(OH)2/graphite nanosheet composites as electro-active materials for supercapacitors is investigated by a galvanostatic charge–discharge method. As expected, the as-prepared α-Ni(OH)2/graphite nanosheet composite exhibits large specific capacitance, good rate capability and long cycle stability as compared to the pure α-Ni(OH)2. Apparently, the unique structure of fine α-Ni(OH)2 nanocrystals fabricated on the matrix of graphite nanosheets is responsible for the improvement of the reaction kinetics and subsequent electrochemical performance of the composite.