Synergistic catalysis of Au-Co@SiO₂ nanospheres in hydrolytic dehydrogenation of ammonia borane for chemical hydrogen storage

Core–shell structured Au-Co@SiO₂ nanospheres have been synthesized using a reverse-micelle method. During heat treatment in vacuum, multiple Au-Co nanoparticles (NPs) embedded in SiO₂ nanospheres (Au-Co@SiO₂-RT) merged into single Au-Co NPs in SiO₂ (Au-Co@SiO₂-HT), resulting in a size increase of the Au-Co NPs. The Au-Co@SiO₂-HT nanospheres showed better catalytic activity than that of Au-Co@SiO₂-RT. The higher catalytic activity of Au-Co@SiO₂-HT could be attributed to the decrease in the content of basic ammine by the decomposition of metal ammine complexes during the heat treatment. Compared with their monometallic counterparts, the bimetallic Au-Co NPs embedded in a SiO₂ nanosphere show higher catalytic activity for the hydrolytic dehydrogenation of NH₃BH₃ to generate a stoichiometric amount of hydrogen at room temperature for chemical hydrogen storage. The synergistic effect between Au and Co inside the silica nanospheres plays an important role in the catalytic hydrolysis of NH₃BH₃.