Acetylene selective hydrogenation over different size of Pd-modified Cu cluster catalysts: Effects of Pd ensemble and cluster size on the selectivity and activity

Aiming at identifying the effects of Pd ensemble and cluster size on the selectivity and activity of C2H2 selective hydrogenation over Pd-modified Cu nano-cluster catalysts, the catalytic performance of C2H2 selective hydrogenation over different cluster sizes of Pd-modified Cu catalyst with different Pd ensemble are examined using density functional theory calculations. A new evaluation method of the C2H4 selectivity is defined. The results indicate that the promoter Pd cannot improve C2H4 selectivity and activity over the small-sized Cu-13 and the large-sized Cu-55 clusters. Only when Cu catalyst has a moderate size such as Cu-38 cluster, the Pd ensemble composed of outer shell with 6 coordination and its contiguous inner-layer Pd atoms can significantly improve C2H4 selectivity and activity. This study provides a theoretical clue for the design of highly efficient and cost-effective noble promoter-modified Cu-based catalysts by controlling the cluster size and the promoter ensemble for C2H2 selective hydrogenation.