Interaction of Ethylene with Irn (n=1-10): From Bare Clusters to γ-Al2O3-Supported Nanoparticles

Comprehending the bond nature of ethylene-metal clusters at the atomic level is important for the design of nanocatalysts and their applications in the fields of fine chemistry and petroleum refining. The growth of Ir-n (n = 1-10) on gamma-Al2O3(110) and ethylene adsorption on bare and gamma-Al2O3(110)-supported Ir-n (n = 1-10) clusters were investigated using the density functional theory (DFT) approach. The mode stability of ethylene adsorption on the bare Ir-n clusters followed the order pi > di-sigma > B-T, with the exception of Ir-8 where the pi structure was less stable than the di-sigma configuration. On supported Ir-n (n = 4-7 and 10) the stability sequence was pi > di-sigma > di-sigma ' (at interface), while on supported Ir-n (n = 2, 3, 8, and 9) the sequence changed to di-sigma > pi > di-sigma ' (at interface). Two-thirds of ethylene adsorption on the supported Ir-n clusters were weaker than its adsorption on the bare Ir-n clusters. The pre-adsorbed ethylene at the interface was found to facilitate the nucleation from the even-sized supported Ir-n to odd-sized Ir-n clusters, but hindered the nucleation from the odd-sized Ir-n to even-sized Ir-n clusters.