Facile synthesis of near-monodisperse Ag@Ni core–shell nanoparticles and their applicationfor catalytic generation of hydrogen

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Magnetically recyclable Ag–Ni core–shell nanoparticles have been fabricatedvia a simple one-pot synthetic route using oleylamine both as solvent andreducing agent and triphenylphosphine as a surfactant. As characterized bytransmission electron microscopy (TEM), the as-synthesized Ag–Ni core–shellnanoparticles exhibit a very narrow size distribution with a typical size of14.9 ± 1.2 nm and a tunable shell thickness. UV–vis absorption spectroscopy study shows thatthe formation of a Ni shell on Ag core can damp the surface plasmon resonance(SPR) of the Ag core and lead to a red-shifted SPR absorption peak. Magneticmeasurement indicates that all the as-synthesized Ag–Ni core–shell nanoparticlesare superparamagnetic at room temperature, and their blocking temperaturescan be controlled by modulating the shell thickness. The as-synthesized Ag–Nicore–shell nanoparticles exhibit excellent catalytic properties for the generation ofH2 from dehydrogenation of sodium borohydride in aqueous solutions. The hydrogengeneration rate of Ag–Ni core–shell nanoparticles is found to be much higher than that ofAg and Ni nanoparticles of a similar size, and the calculated activation energyfor hydrogen generation is lower than that of many bimetallic catalysts. Thestrategy employed here can also be extended to other noble-magnetic metal systems.