Density Functional Theory Study on the Role of Polyacetylene as a Promoter in Selective Hydrogenation of Styrene on a Pd Catalyst

Understanding mechanisms of catalyst–substrate interactions is of essential importance for the design and development of novel catalysts with superior performances. In the present density functional theory study, selective hydrogenation of styrene on a polyacetylene (PA)-supported Pd4 catalyst (Pd4/PA) was employed as a model system to address how catalyst–substrate interactions affect the charge state of Pd, which subsequently influences catalytic activity. It was found that the Pd cluster can be anchored strongly on the C═C bond of the polymer substrate through the π–d interaction, which further leads to charge rearrangement on the Pd4 cluster with the top two Pd atoms being more negatively charged. By comparing the calculated minimum energy profiles of styrene hydrogenation on surfaces of both pure Pd4 and Pd4/PA, the mechanism that dictates the catalytic process on Pd4/PA was identified. Charge analysis reveals that the enhanced catalytic activity of Pd4/PA is largely attributed to the negative charge...