Do Olefin Hydrogenation Reactions Remain Structure Insensitive over Pt in Nanostructured Pt-on-Au Catalyst?

Understanding the effects of catalyst surface structure on a catalytic reaction is of fundamental importance in catalysis chemistry. Herein, a series of Pt-on-Au (Pt_m^Au, m refers to the atomic Pt/Au ratio; Au size: 3.2 ± 0.4 nm) nanostructures with Pt dispersion in the range of 38% to 100% are used to study the structure sensitivity of the hydrogenation reactions of 1,3-butadiene and ethylene, respectively. The specific catalytic rates for both reactions are observed to increase with a decrease in the Pt dispersion or increasing m in Pt_m^Au, demonstrating the structure-sensitive nature of both reactions over the Pt_m^Au nanostructures. These observations strongly contrast with the structure insensitivity of the same reactions over our deliberately prepared counterpart Pt/SiO₂ catalysts with Pt dispersion varying in 6%∼100% and also those documented in literature and thus identify a distinct feature of Pt in the Pt_m^Au nanostructures. Characterization results from XANES spectroscopy and DRIFTS of adsorbed CO show that the variation of Pt dispersion or m in Pt_m^Au resulted in systematical changes in the electronic property of Pt, which uncover the nature of the structure sensitivity. These findings would have important implications for better understanding the dimension and richness of the structure-sensitivity concept and the features of Pt-on-Au nanostructures in catalysis and nanomaterial chemistry, as well as its related fields.