CO oxidation at Pd(100): A first-principles constrained thermodynamics study

The possible formation of oxides or thin oxide films (surface oxides) on late transition-metal surfaces has recently been recognized as an essential ingredient when aiming to understand catalytic oxidation reactions under technologically relevant gas phase conditions. Using CO oxidation at Pd(100) as an example, we investigate the composition and structure of this model catalyst surface over a wide range of (T,p) conditions within a multiscale modeling approach where density-functional theory is linked to thermodynamics. The results show that under the catalytically most relevant gas phase conditions a thin surface oxide is the most stable "phase" and that the system is actually very close to a transition between this oxidic state and a reduced state in terms of a CO-covered Pd(100) surface.