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An oleylamine-assisted solvothermal approach has been developed for the synthesis of nickel hydroxide nanomaterials. α-Ni(OH)2 flower-like spheres and β-Ni(OH)2 hexagonal sheets were obtained by tuning the water volume in the synthesis system. The water-induced phase and morphology evolution from α-Ni(OH)2 spheres to β-Ni(OH)2 sheets were investigated in detail by controlled experiments based on their crystal structures. Moreover, NiO spheres and sheets were obtained by direct thermal decomposition of corresponding nickel hydroxides. N2 adsorption/desorption, temperature-programmed reduction with H2, and catalytic activity tests reveal that NiO spheres exhibit higher surface area, larger pore volume, higher reducibility, and better catalysis activities for CO oxidation than NiO sheets.

A facile one-step strategy has been developed for preparing monodisperse CeO(2) mesoporous spheres with high surface areas, uniform size distributions, and well-defined pore topologies. These mesoporous spheres have been demonstrated to be catalytically stable and active for CO oxidation.

Hierarchiral NiO flower-like microspheres with tunable porosity were prepared based on a facile solvothermal method. Three kinds of NiO micro-flowers (NiO-A, NiO-B, and NiO-C) with different porosity have been fabricated mainly by tuning the concentration of nickel nitrate. These flower-like microspheres are comprised of densely packed irregular sheets and display a multi-peaks pore distribution in a wide range in both mesoporous and macroporous regions. The BET surface area of NiO-A, NiO-B and NiO-C is 59.9 m2 g−1, 50.2 m2 g−1 and 15.1 m2 g−1, respectively. The pore volume of NiO-A, NiO-B and NiO-C is 0.2214 cm3 g−1, 0.0829 cm3 g−1 and 0.0549 cm3 g−1, respectively. These NiO spheres show a strong morphology dependant nature for CO oxidation catalysis. Compared to the conventional NiO nanoparticles, these flower-like NiO micro-spheres possess a superior catalytic activity for CO oxidation.