2014 Volume 93 Issue 8 Pages 703-709
We study the effect of solvents on morphological and/or structural properties and catalytic activity of hollow nickel-silica composite spheres for hydrolytic dehydrogenation of ammonia borane. Nickel-silica composite shells were coated on polystyrene (PS) templates via sol-gel reaction with L(+)-arginine as the promoter of the sol-gel reaction followed or in parallel with the dissolution of the PS templates in the same medium to form hollow spheres. From the transmission electron microscopy (TEM) images, nickel-silica composite shells were formed for 1.5 h, and the surface roughness of the shells increases with the increase of aging time in methyl alcohol, while the shells were formed via the formation of aggregates of irregular shape in ethyl alcohol and 2-propyl alcohol. From the angle attenuated total reflectance infrared (ATR-IR) spectra, the order of dissolution rate of PS templates is 2-propyl alcohol > ethyl alcohol > methyl alcohol. These results indicate that the shells are formed before the dissolution of PS templates in methyl alcohol, while in ethyl alcohol and 2-propyl alcohol, nickel-silica composite shells was formed in parallel with dissolution of PS templates via the formation of aggregates of irregular shape. From the results of N2 adsorption/desorption isotherm analysis, the order of BET surface area is samples prepared in ethyl alcohol > methyl alcohol ≈ 2-propyl alcohol. The catalytic activity for hydrolytic dehydrogenation from aqueous NaBH4/NH3BH3 solution in the presence of the hollow spheres prepared in ethyl alcohol was much higher than those in the presence of the hollow spheres prepared in methyl alcohol and 2-propyl alcohol. Consequently, the solvents were mainly influenced in morphological homogeneity and BET surface area of hollow nickel-silica composite spheres, and these structural properties affected the catalytic activity.