L-Lysine assisted synthesis of β-Ni(OH)2 hierarchical hollow microspheres and their enhanced electrochemical capacitance performance

Hierarchical beta-Ni(OH)(2) hollow microspheres with partial open gaps have successfully been prepared via a facile hydrothermal process with the assistance of L-lysine. The as-prepared products have been characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N-2 adsorption/desorption, respectively. The results reveal that the sample consists of a large scale of porous microspheres which is composed of nanosheets. A possible growth mechanism is proposed including the initial formation of hierarchical hollow microspheres aggregated from nuclei and the subsequent site-specific oriented growth of nanosheets by self-assembly along a preferred growth direction of [1 01] at the growth state. It is found that L-lysine used as a crystal growth modifier plays a key role in the formation of this hierarchical structure. This special structure is also responsible for the obvious enhancement of electrochemical properties, which exhibits a high specific capacitance of 1398.5 F g(-1) at a current density of 5 mA cm(-2) and excellent cycling stability. This hollow microspheres display great potential as electrode materials for electrochemical capacitors. (C) 2012 Elsevier Ltd. All rights reserved.