Abstract: Low-cost and high-performance catalyst is crucial for hydrogen generation via the hydrolysis of ammonia borane (NH₃BH₃, AB) as a chemical hydrogen storage material. In this work, Co-CeO_x nanocomposites supported on graphene (Co-CeO_x/graphene) were prepared through a facile impregnation and chemical reduction method and used as a catalyst in the hydrolytic dehydrogenation of ammonia borane. The results indicate that the as-prepared Co-CeO_x/graphene nanocomposite exhibits superior catalytic activity and recycling stability in the hydrolysis of ammonia borane, owing to the ultra-fine size of Co-CeO_x particles, the strong synergistic electronic effect between Co and CeO_x, as well as the strong metal-support interaction between Co-CeO_x and graphene. For the hydrolysis of ammonia borane over the optimized Co-CeO_x/graphene catalyst, the turnover frequency (TOF) reaches 45.1 min⁻¹, with the activation energy (E_a) of 39.5 kJ/mol; such a TOF value is 12 times and 9 times higher than those over Co and Co/graphene, respectively, also much higher than those reported for most noble-metal-free catalysts.