pH-dependant structural and morphology evolution of Ni(OH)2 nanostructures and their morphology retention upon thermal annealing to NiO

► Nickel hydroxide nanosheets, nanobelts, and nanorods, were prepared by hydrothermal crystallization of amorphous precipitates. ► The pH value at precipitation is the key to determine the crystal structure and morphology of the Ni(OH)2 formed. ► Nanosheets of hexagonal β-Ni(OH)2 are formed at pH ∼ 11, and in the pH range 9.5-8.5, α-Ni(OH)2 nanobelts and nanorods can be obtained. ► Air annealing of the as-prepared Ni(OH)2 yields NiO nanostructure of almost similar morphology as their hydroxide precursors.