Ru@Ni core-shell nanoparticles (NPs) supported on graphene have been synthesized by one-step in situ co-reduction of aqueous solution of ruthenium (III) chloride, nickel (II) chloride, and graphene oxide (GO) with ammonia borane (AB) as the reducing agent under ambient condition. The as-synthesized NPs exhibit much higher catalytic activity for hydrolytic dehydrogenation of AB than the monometallic, bimetallic alloy (RuNi/graphene), and graphene-free core-shell (Ru@Ni) counterparts. Additionally, the Ru@Ni/graphene NPs facilitate the hydrolysis of AB, with the turnover frequency (TOP) value of 340 mol H-2 min(-1) (mol Ru)(-1), which is among the highest value reported on Ru-based NPs so far, and even higher than the reversed Ni@Ru NPs. Furthermore, the as-prepared NPs exert satisfied durable stability and magnetically recyclability for the hydrolytic dehydrogenation of AB and methylamine borane (MeAB). Moreover, this simple synthetic method can be extended to other Ru-based bimetallic core-shell systems for more applications. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.