Two kinds of Co-Mo bimetallic catalysts (i.e., CoMo-I/gamma-Al2O3 and CoMo-II/gamma-Al2O3) prepared by using different active phase precursors as well as Co and Mo monometallic catalysts were used to catalyze ammonia decomposition. The Co-Mo bimetallic catalysts show higher activity than the Co and Mo monometallic catalysts, indicating the synergistic effect between Co and Mo. More interestingly, the CoMo-I/gamma-Al2O3 catalyst using monocomponent metal amine metallate (i.e., Co(en)(3)MoO4) as the active phase precursor exhibits higher activity and stability than the CoMo-II/gamma-Al2O3 using bicomponent Co(NO3)(2) and (NH4)(6)Mo7O24 as the active phase precursor, which could be linked to the higher content of active species CO3Mo3N for the CoMo-I/gamma-Al2O3 catalyst. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.