The synthesis and characterization of AuPd nanoparticle catalysts for systematically investigating the effects of bimetallic interactions on catalytic performance

Heterogeneous catalysts save energy in industrial chemical processes by lowering the temperature of reaction and avoiding waste production. Platinum group metals are the state of the art in catalysis, but are also costly and scarce. The use of bimetallic nanoparticles minimizes the amount of PGM needed, and often enhances catalytic performance. Our understanding of how two metals interact to improve catalysis is limited, however, by our ability to control the structure of the catalysts studied, especially regarding the metal distribution. The work here presents the synthesis of a set of 5 nm Aucore-Pdshell nanoparticles which have shells 0.7, 1.9, and 3.8 monolayers thick, and alloyed particles of equal composition (10, 20, and 28% Pd, respectively) that are of catalytically-relevant size. These have been characterized using electron microscopy and surface science techniques. It was found that the presence of Au inhibits sintering of the particles during heating, and that the core-shell particles can be tuned to hold H2 in the bulk. The alloys were used in limonene dehydrogenation to test how composition affects catalyst selectivity, and the core-shell and alloy catalysts were used in ethylene hydrogenation to probe how elemental composition and ordering change catalyst activity.