Geometric Requirements for Hydrocarbon Catalytic Sites on Platinum Surfaces

Abstract

Vibrational spectroscopic measurements and density functional calculations were used to identify a preferential catalytic mechanism for the transformation of acetylene, HCCH, to vinylidene, CCH2, on surfaces of Pt‐Sn ordered alloys. In this mechanism, two adjacent Pt atoms adsorb an acetylene molecule and a third neighboring Pt atom is required for stabilizing the reacting H atom during the transformation. Therefore, unlike a direct H shift along the CC bond in organometallic compounds with a single transition‐metal atom, this mechanism has a geometric site requirement of three adjacent Pt atoms in the form of a three‐fold site. The same geometric site requirement is identified for preferential CH bond cleavage of acetylene with the formation of adsorbed CCH and H species. In the absence of three‐fold Pt sites, the reaction mechanism changes, and reactions of H transfer and CH bond cleavage are suppressed.

Individual Heat of Adsorption of Adsorbed CO Species on Palladium and Pd–Sn Nanoparticles Supported on Al2O3 by Using Temperature-Programmed Adsorption Equilibrium Methods

“…This decrease seems a priori unfavorable to the hydrogenation reaction. However, others favorable surface processes can be operant on the bimetallic particles such as hydrogen spillover, ,, dissociation on single metal atom, and specific site geometries, , which must be taken into account in the development of the EMA.…”