Cobalt hollow nanospheres: controlled synthesis, modification and highly catalytic performance for hydrolysis of ammonia borane

Size tunable cobalt hollow nanospheres with high catalytic activity for the ammonia borane (AB) hydrolysis have been synthesized by using the solvothermal method. The complexation between Co 2+ and ethylenediamine is observed to be critical for the formation of the cobalt hollow nanospherical structure. The morphology of the cobalt hollow nanospheres can be regulated by adjusting the original ethylenediamine/ethanol volume ratio, reaction time and temperature. Impressively, the magnetic property study reveals that the coercivity of the as-synthesized cobalt hollow nanospheres is much enhanced compared with that of bulk cobalt materials. Meanwhile, Co/Pt bimetal hollow nanospheres (CoPtHS) and graphene-cobalt hollow composite nanospheres (CoHS-rGO) have also been explored. In comparison with the cobalt hollow nanospheres, both the CoPtHS and CoHS-rGO show higher catalytic activities and better repeatability for the catalytic hydrogen generation from AB hydrolysis. Moreover, it is noted that these catalysts could be recycled by using the magnetic separation method.