Core–shell structured Au-Co@SiO2 nanospheres have been synthesized using a reverse-micelle method. During heat treatment in vacuum, multiple Au-Conanoparticles (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 hydrogenstorage. The synergistic effect between Au and Co inside the silica nanospheres plays an important role in the catalytichydrolysis of NH3BH3.