Nanoparticle Shape Dictates Catalytic Performance in Selective Hydrogenation of Butadiene Over Au-Pd Core-Shell Nanoparticles

Abstract

Selective hydrogenation of butadiene is a critical step in purification of alkene feedstocks for polymer production and is traditionally catalyzed by Pd-based materials. In bimetallic Pd catalysts, the metal distribution largely impacts the catalytic performance, with a core-shell structure being the most favorable atomic arrangement. Yet, little is known about the impact of nanoparticle shape on the activity and selectivity of these core-shell catalysts, and how their crystal structure controls the functional properties. In this work, we demonstrate the importance of the nanoparticle shape and the type of surface facets on the catalytic reactivity of Au-core Pd-shell nanocatalysts in the selective hydrogenation of butadiene. We employed colloidal synthesis to prepare well-defined Au-Pd core-shell nanorods and nanospheres with 2 and 5 Pd-shell layers. The nanorods have {110} and {100} surface facets while the nanospheres consist of mostly {111} facets. We demonstrate that Au-core Pd-shell nanospheres outperform the nanorods in activity, and that spheres with 2 Pd-shell layers exhibit the highest selectivity. Our complementary hydrogen-deuterium exchange measurements reveal that the favorable performance of the nanospheres is linked to a higher hydrogen dissociation rate over the {111} facets. Altogether, our study aids the design of shape-controlled nanocatalysts for selective hydrogenation catalysis.