Oxide coated nickel powder as support for platinum(0) nanoparticles: Magnetically separable catalysts for hydrogen generation from the hydrolysis of ammonia borane

We report the development of a novel method for the preparation of magnetically separable platinum nanoparticles. Magnetic nickel nanopowder is initially synthesized in a radiofrequency plasma reactor where in-line passivation was carried out with oxygen gas, resulting in the formation of nickel oxidecoated nickel particles. Following this, platinum nanoparticles are deposited onto the surface of the oxidecoated nickel nanopowder, forming Pt-0/Ni@NiO nanocatalysts for the hydrolytic dehydrogenation of ammonia borane. The Pt-0/Ni@NiO nanoparticles, containing 0.24 % wt. Pt, exhibit remarkable catalytic activity in the hydrolytic dehydrogenation of ammonia borane, with a turnover frequency of 468 (mol H-2)x(mol Pt)(-1) x min(-1) for releasing 3 equivalent H-2 gas per mole of ammonia borane from its hydrolysis at 25 degrees C. This heightened catalytic activity of Pt-0/Ni@NiO nanoparticles is attributed to the favorable metal-support interaction between the platinum(0) nanoparticles and oxide surface, namely the bonding of platinum to the oxide surface, as elucidated by the XPS analysis. More importantly, Pt-0/Ni@NiO nanoparticles can be separated from the reaction solution by using an external magnet.