CO oxidation on Pd(100) at technologically relevant pressure conditions: A first-principles kinetic Monte Carlo study

Abstract

The possible importance of oxide formation for the catalytic activity of transition metals in heterogenous oxidation catalysis has evoked a lively discussion over the recent years. On the more noble transition metals (like Pd, Pt or Ag) the low stability of the common bulk oxides suggests primarily sub-nanometer thin oxide films, so-called surface oxides, as potential candidates that may be stabilized under gas phase conditions representative of technological oxidation catalysis. We address this issue for the Pd(100) model catalyst surface with first-principles kinetic Monte Carlo (kMC) simulations that assess the stability of the well-characterized (sqrt{5} x sqrt{5})R27 surface oxide during steady-state CO oxidation. Our results show that at ambient pressure conditions the surface oxide is stabilized at the surface up to CO:O2 partial pressure ratios just around the catalytically most relevant stoichiometric feeds (p(CO):p(O2) = 2:1). The precise value depends sensitively on temperature, so that both local pressure and temperature fluctuations may induce a continuous formation and decomposition of oxidic phases during steady-state operation under ambient stoichiometric conditions.

13 pages including 5 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.html

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• Multi-Lattice Kinetic Monte Carlo Simulations from First-Principles: Reduction of the Pd(100) Surface Oxide by CO
• CO oxidation on Pd(100) vs. PdO(sqrt5xsqrt5)R27^o: First-Principles Kinetic Phase Diagrams and Bistability Conditions
• Accelerating the prediction of inorganic surfaces with machine learning interatomic potentials
• Model for the catalytic oxidation of CO, including gas-phase impurities and CO desorption
• Monte Carlo Simulations of the Critical Properties of a Ziff-Gulari-Barshad model of Catalytic CO Oxidation with Long-range Reactivity
• A model for the catalytic oxidation of CO that includes CO desorption and diffusion, O repulsion, and impurities in the gas phase
• Structure Sensitivity in Oxide Catalysis: First-Principles Kinetic Monte Carlo Simulations for CO Oxidation at RuO${}_2$(111)
• Thermodynamically Consistent Incorporation of the Langmuir Adsorption Model into Compressible Fluctuating Hydrodynamics