Fabrication of hollow silica–alumina composite spheres and their activity for hydrolytic dehydrogenation of ammonia borane

In this study, we investigated the influence of the preparation conditions of hollow silica–alumina composite spheres on their activity for the hydrolytic dehydrogenation of ammonia borane. Hollow silica–alumina composite spheres were prepared by polystyrene template method, and the polystyrene template particles were removed by calcination. The as-prepared hollow spheres were calcined at 523–873 K for 3 h. From the results of elemental analysis, polystyrene templates were completely removed by calcination at 873 K. small particles around the hollow spheres were observed from the images of transmission electron microscopy. To obtain homogeneous hollow spheres, the as-prepared hollow spheres were calcined at 873 K for 0–12 h. From the results of transmission electron microscopy, homogeneous hollow spheres were obtained by calcination for 0 h. The activity of the hollow spheres was the 2.6 times higher that of the hollow spheres calcined for 3 h. From the results of activity tests and ammonia temperature-programming desorption, the activity of the hollow spheres depends on amount of acid sites.