Noble metal nanoparticles enclosed by well-defined surface facets are promising catalytic materials for selective chemical transformations due to the differing binding strength and orientation of adsorbed precursors on surfaces with different atomic arrangements. In addition, the incorporation of a small amount of one metal into a surface composed of a second metal has also been shown to affect the adsorption and reactivity of reactant species, thus influencing selectivity. By manipulating the relative reduction kinetics of two different metal precursors through the tailored selection of a reducing agent, fine tuning of solution pH, and the introduction of additives such as halides, we have synthesized shaped bimetallic nanostructures with well-defined, faceted surfaces. In addition to kinetic effects resulting from differences in the reduction rates of the two metal precursors, under certain conditions, selective surface passivation is the driving factor for shape control. In this case, the selective deposition of a submonolayer of one metal onto specific facets on a growing nanoparticle of a second metal yields shaped nanostructures composed primarily of one metal with a submonolayer surface coverage of another metal. This concerted tuning of facet structure and surface composition opens up promising avenues to the design of selective catalysts for partial oxidation and partial hydrogenation reactions.

Polyhedral metal nanoparticles with bimetallic surfaces: Kinetic control and surface passivation

253rd National Meeting (2017)

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