Formation of hollow NiO single crystals and Ag/NiO flowers

In this work, the Ni(OH)2 core–shell nanostructures were fabricated by a hydrothermal method without using any templates. After the core–shell sample was annealed, the novel hollow NiO nanostructures were obtained. The Ostwald ripening process was proposed to elucidate the formation of the samples. Moreover, Ag/NiO flowers were prepared by impregnating hollow NiO particles with Ag(NO3)3 solution. The samples were characterized by TEM, HREM, SAED, XRD, BET, SEM and EDS methods. Most importantly, Ag/NiO flowers and hollow NiO nanostructures exhibited the excellent catalytic activities for CO oxidation.