Template-free synthesis of NiO hollow microspheres covered with nanoflakes

α-Ni(OH)2 hollow microspheres precursors were synthesized without any template through a solvothermal method. Hydrolyzing NiCl2 in alkaline solution, the Ni(OH)2 hollow microspheres covered with a disordered covering of perpendicular nanoflakes were prepared. Subsequently, the similar microstructured NiO hollow microspheres with BET area around 222.8 m2/g and specific pore volume around 0.5 cm3/g were obtained by calcining the above precursor at 250–300 °C with a slow heating rate (about 1 K/min). The effects of the surfactant and the calcining temperature on the morphology and the mesostructure of the NiO hollow microspheres were also discussed.