A facile method for the preparation of nearly monodisperse Ru nanoparticles (NPs) and their record catalytic activity in the hydrolytic dehydrogenation of ammonia borane (AB) for chemical hydrogen storage are reported herein. Ru NPs were prepared by a novel protocol comprising the thermal decomposition and concomitant reduction of ruthenium(III) acetylacetonate (Ru(acac)(3)) in the presence of oleylamine (OAm) and benzylether (BE). In the protocol, OAm served as both a stabilizer and reducing agent and BE used as a solvent. Ru NPs were supported on aluminum oxide nanopowder (Ru@Al2O3) via a simple liquid impregnation method before their use as catalyst for the dehydrogenation of AB in water. Without any special treatment to remove the surfactants, Ru@Al2O3 showed high catalytic activity in the hydrolytic dehydrogenation of AB providing an initial turnover frequency (TOF) of 39.6 mol H-2 (mol Ru min)(-1). Their catalytic performance was further enhanced dramatically by the acetic acid treatment and the initial TOF value is increased to 83.3 mol H-2 (mol Ru min)(-1) that is the highest among the reusable Ru catalysts and even higher than Pt-based catalysts tested in the hydrolysis of AB. Additionally, the work reported here includes a wealth of kinetic data to determine the rate law and apparent activation parameters for the catalytic dehydrogenation of AB in water. (C) 2012 Elsevier B.V. All rights reserved.