The Phase and Morphology of Hydrothermally Synthesized Nanostructured Nickel/nickel Hydroxides and Their Supercapacitor Application

Urchin-like nanostructured nickel/nickel hydroxides (NNHO) were successfully synthesized by using the hydrothermal method, and the phase and the morphology of the nanostructured nickel/nickel hydroxide were controlled by using different synthesis temperatures. The diameter of the nanostructured NNHO synthesized at a relatively high temperature wes bigger than that of the samples synthesized at low temperature, which could be explained by using Ostwald ripening. The phase of the as-synthesized nanostructure was composed of crystalline metallic nickel on the inside and amorphous nickel hydroxide on the surface. To compare the electrochemical properties, the as-synthesized samples are converted to nickel oxide (NO) by annealing at different temperatures. The as-synthesized NNHO showed the highest specific capacitance, as well as easy electrolyte accessibility, because NNHO had not only an easily accessible nanostructure but also the synergistic effect of crystalline nickel and amorphous nickel hydroxide. The present work can contribute to the synthesis of nanostructured NNHO and to the applications of supercapacitors using heterostructure materials.