Influence of preparation conditions of hollow silica-nickel composite spheres on their catalytic activity for hydrolytic dehydrogenation of ammonia borane

In this paper, we investigated influence of preparation conditions of hollow silica-nickel composite spheres on their morphology and catalytic activity for hydrolytic dehydrogenation of ammonia borane. In the preparation method of this study, when silica-nickel composite shells were coated on polystyrene templates by the sol-gel method using L(+)-arginine as the promoter for the reaction to form silica-nickel composite shell, the polystyrene templates were dissolved subsequently, even synchronously, in the same medium to form hollow spheres. The as-prepared silica-nickel composite spheres were characterized by transmission electron microscopy and scanning electron microscopy. The effects of Si+Ni content on the morphology were systematically evaluated. All the as-prepared hollow silica-nickel composite spheres have the similar morphology as identified by SEM and TEM measurement. Homogeneity of the hollow silica-nickel composite spheres increases with the increase in the Si+Ni content as shown by the laser diffraction particle size analysis. The catalytic activities of the hollow silica-nickel composite spheres for hydrolytic dehydrogenation of ammonia borane prepared with different Si+Ni contents were compared. The catalytic activity for the hydrogen evolution in the presence of the hollow spheres increases with the increase of Si+Ni content. The results of FTIR spectra of the hollow silica-nickel composite spheres indicate that a certain amount of residual PS templates exists in hollow silica-nickel composite spheres. The residual PS templates was able to be reduced by procedure of as-prepared samples with toluene solvent. The catalytic activity of hollow silica-nickel composite spheres increases with decrease in the amount of residual PS templates. (C) 2013 Elsevier B. V. All rights reserved.