Author:

Keywords:

Modeling, Monte Carlo, Simulation, surface segregation, alloys, catalyst

Abstract:

The effect of local atomic order and of surface composition on the activity of the bimetallic model catalyst Cu 3Pt(111) for the CO oxidation reaction was evaluated. A semi-empirical modeling approach was used with Kinetic Monte Carlo (KMC) simulations, which allowed for a microscopic description of the catalytic process. The KMC simulations were combined with parameterized models for the metal-adsorbate bond energies and for the lateral interaction energy between adsorbates. The KMC simulations at various conditions of temperature and pressure revealed a higher reaction rate on the ordered Cu 3Pt(111) surface than on the disordered Cu 40Pt 60(111) surface. At 400 K, the CO 2 turnover frequency was ∼ 3 times higher on ordered Cu 3Pt(111) compared to that on Cu 40Pt 60(111). This lower reaction rate on the disordered surface could be explained by two effects. Firstly, the CO binds less strongly to the disordered Cu 40Pt 60(111) surface, resulting in a lower CO coverage. Secondly, the activation barrier for O displacement from fcc sites to bridge sites was, on average, larger on the disordered Cu 40Pt 60(111) surface. This is an abstract of a paper presented at the 18th International Congress of Chemical Process Engineering (Praque, Czech Republic 8/24-28/2008).