Hydrous hydrazine (H2NNH2 center dot H2O) has generally been considered a promising hydrogen storage carrier because of inherent advantages such as its high hydrogen content and easy recharging as a liquid. Unfortunately, the decomposition of hydrous hydrazine to H-2 is terribly sluggish and/or not entirely favored-a competing decomposition to ammonia may be preferred. This has been the case using noble-metal catalysts and using non-precious-metal- based catalysts, even at elevated temperatures. To overcome this challenge, non-precious-metal-based Cu@Fe5Ni5 core@shell nanocatalysts are prepared using an in situ seeding-growth approach. Unexpectedly, the catalyst exerts 100% H-2 selectivity and excellent activity and stability toward the complete decomposition of hydrous hydrazine, which is due to the synergistic effect of the core@shell structure. These promising results will certainly promote the effective application of hydrous hydrazine as a potential hydrogen storage material.