The modulation mechanism of geometric and electronic structures of bimetallic catalysts: Pd13−mAgm (m=0–13) clusters for acetylene semi-hydrogenation

Abstract

The modulating mechanism of the second metal in bimetallic catalysts for the catalytic properties has always been a hot topic. Pd_13−mAg_m (m=0–13) clusters are used as the model catalysts to explore the influence of Ag-induced configurational and electronic evolution of the PdAg phase on the catalytic performance of acetylene semi-hydrogenation by theoretical calculations. From the results obtained, it can be found that the activity/selectivity to ethylene dramatically depends on the geometric and electronic structures of 13-atom bimetallic clusters in the subnanometer size regime. The adsorption configuration of the C₂ species is determined by the structure of bimetallic clusters, which can be attributed to the reasonable matching with the highest occupied molecular orbital (HOMO). A metastable composition Pd₆Ag₇ cluster, exhibiting the biggest difference in electrons supplied from the clusters to acetylene and ethylene, promotes the reaction path of the target product in the semi-hydrogenation of acetylene. The modulating mechanism of silver has been deeply explored in this paper, which will provide important theoretical guidance for the rational design and development of bimetallic catalysts.