title: Microwave synthesis of classically immiscible rhodium-silver and rhodium-gold alloy nanoparticles: highly active hydrogenation catalysts.
abstract: Noble metal alloys are important in large-scale catalytic processes. Alloying facilitates fine-tuning of catalytic properties via synergistic interactions between metals. It also allows for dilution of scarce and expensive metals using comparatively earth-abundant metals. RhAg and RhAu are classically considered to be immiscible metals. We show here that stable RhM (M = Ag, Au) nanoparticles with randomly alloyed structures and broadly tunable Rh:M ratios can be prepared using a microwave-assisted method. The alloyed nanostructures with optimized Rh:M compositions are significantly more active as hydrogenation catalysts than Rh itself: Rh is more dilute and more reactive when alloyed with Ag or Au, even though the latter are both catalytically inactive for hydrogenation. Theoretical modeling predicts that the observed catalytic enhancement is due to few-atom surface ensemble effects in which the overall reaction energy profile for alkene hydrogenation is optimized due to Rh-M d-band intermixing.
authors.affiliation: Department of Chemistry, The University of Texas at Austin , Welch Hall 2.204, 105 East 24th Street Stop A5300, Austin, Texas 78712-1224, United States.
authors.forename: Stephany
authors.initials: S
authors.lastname: García
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.forename: Graham W
authors.initials: GW
authors.lastname: Piburn
authors.forename: Graeme
authors.initials: G
authors.lastname: Henkelman
authors.forename: Simon M
authors.initials: SM
authors.lastname: Humphrey
keywords: alloy nanoparticles; density functional theory (DFT); heterogeneous catalysis; hydrogenation; immiscible alloys; microwave synthesis