Abstract
In the present work, we investigated the influence of the pore structure of molybdic acid-immobilized silicaalumina hollow spheres on their activity towards acid-promoted hydrogen evolution from aqueous ammonia borane solution. To control the pore structure, a surfactant, cetyltrimetylammonium bromide, and a swelling agent, 1-dodecylamine, were used during the shell formation of the hollow spheres. The amount of surfactant and swelling agent were found to influence the amount of mesopores formed. Further, the crystallinity of the immobilized molybdic oxide species as well as the ratio of inactive mixed oxides of aluminum and molybdenum decreased with increasing amounts of the surfactant and swelling agent. The immobilized hollow spheres with the high dispersed molybdic oxide and the inactive mixed oxide ratio also exhibited high activity towards hydrogen evolution from aqueous ammonia borane solution. The crystallinity of molybdic oxide tended to decrease with a decrease in the amount of immobilized molybdic acid. Furthermore, the hollow spheres with low molybdic oxide content exhibited high activity towards hydrogen evolution.
