Synthesis and catalysis properties of NiO flower-like spheres and nanosheets: Water-induced phase transformation of nickel hydroxides

摘要

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. N_2 adsorption/ desorption, temperature-programmed reduction with H_2, 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.