Mixed Aromatic−Alkyne System on a Pd Surface: A First-Principles Study

The chemistry of mixed aromatic-alkyne systems on a metal surface is of general interest in many industrial processes. We use density functional theory (DFT) to investigate the chemistry of one such system (i.e., 1,4-diphenyl-butadiyne (DPB) in contact with Pd(110) and Pd(111) surfaces). Reaction pathways and the energetics of important processes are explored, including H2 adsorption, dissociation and migration on the metal surface, the DPB-metal interaction, the energetics of H uptake, and the effects of impurities such as CO and CO2 on H chemistry. We find that (i) strong aromatic-metal interaction leads to significant binding strength of the DPB molecule to both Pd surfaces, especially the (110); (ii) H2 molecules readily dissociate on the Pd surface into H-radicals, which get taken up by alkyne triple bonds; (iii) CO has strong binding to the metal surface, but interacts weakly with H radicals; and (iv) CO2 binds weakly to the metal surface, but could potentially lead to interesting chemical reactions with H.