Unlocking Synergy in Bimetallic Catalysts by Core-Shell Design

Extending the toolbox from mono- to bimetallic catalysts is key in realizing efficient chemical processes. Traditionally, the performance of bimetallic catalysts featuring one active and one selective metal is optimized by varying the metal composition, often resulting in a compromise between the catalytic properties of the two metals. Here we show that by designing the atomic distribution of bimetallic Au-Pd nanocatalysts, we obtain a synergistic catalytic performance in the industrially relevant selective hydrogenation of butadiene. Our single crystalline Au-core Pd-shell nanorods were up to 50 times more active than their alloyed and monometallic counterparts, while retaining high selectivity. We find a shell thickness dependent catalytic activity, indicating that not only the nature of the surface but also several sub-surface layers play a crucial role in the catalytic performance, and rationalize this finding using density-functional-theory calculations. Our results open up a novel avenue for the structural design of bimetallic catalysts.