Atomistic Simulation Group, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN, U.K. School of Chemistry, Queen's University, Belfast BT9 5AG, U.K.
Ali Alavi , Peijun Hu
November 16, 1998
CO oxidation on Pt(111) is studied with ab initio density functional theory, using plane-waves and pseudopotentials. The low energy pathway and transition state for the reaction CO/ -O/Pt(111) CO /Pt(111) are identified using a constrained minimisation scheme. ( Snaphots of the reaction pathway can be downloaded from . See also ). The transition state consists of the O atom at a bridge site, and the CO molecule at a neighbouring top site, with C-O separation of 2.1Å. The activation energy eV. Approximately 60% of this energy can be accounted for by the O atom moving from the hollow to bridge site ( thereby breaking a O-metal bond), while the remainder is due mainly to placing a CO atom at a top site adjacent to the bridging O atom. The pathway can be rationalised in terms of competition of the O and C atoms for bonding with the underlying surface. It is suggested that the physical origin of the predominant barrier is the strength of the O-metal bond, and modification of this bond strength can be expected to affect crucially the catalytic activity.