Interaction of Ethylene with Ir (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 = 1⁻10) on γ⁻Al₂O₃(110) and ethylene adsorption on bare and γ⁻Al₂O₃(110)-supported Ir (n = 1⁻10) clusters were investigated using the density functional theory (DFT) approach. The mode stability of ethylene adsorption on the bare Ir clusters followed the order π > di-σ > B-T, with the exception of Ir₈ where the π structure was less stable than the di-σ configuration. On supported Ir (n = 4⁻7 and 10) the stability sequence was π > di-σ > di-σ' (at interface), while on supported Ir (n = 2, 3, 8, and 9) the sequence changed to di-σ > π > di-σ' (at interface). Two-thirds of ethylene adsorption on the supported Ir clusters were weaker than its adsorption on the bare Ir clusters. The pre-adsorbed ethylene at the interface was found to facilitate the nucleation from the even-sized supported Ir to odd-sized Ir clusters, but hindered the nucleation from the odd-sized Ir to even-sized Ir clusters.