On-site ammonia (NH3) decomposition is considered as a potential path to supply COx-free hydrogen for fuel cell vehicles. In this article, monometallic catalysts (Fe, Co, Ni, and Mo) and bimetallic catalysts (Fe-Co, Mo-Co, Fe-Ni, and Mo-Ni) were prepared and tested in plasma-catalytic NH3 decomposition, where 6Fe-4Ni catalyst exhibited the highest activity and synergistic capability with plasma. At 500 degrees C, NH3 were completely decomposed (>99.9% NH3 conversion); the rate of H-2 production and the energy consumption of H-2 production reached 0.96mol g(-1) h(-1) and 0.050kW h (mol g(-1))(-1), respectively. The 200h continuous operation results indicate an excellent durability of 6Fe-4Ni catalyst. The catalysts characterization and plasma diagnosis results indicate that NH3 was pre-activated by plasma into excited-state species (NH3, NH2, and NH), and the 6Fe-4Ni catalyst exhibited the highest capability to adsorb excited NH3, NH2, and NH species, which could be the main reason why 6Fe-4Ni catalyst exhibited the highest activity. (c) 2018 American Institute of Chemical Engineers AIChE J, 65: 691-701, 2019