Beyond Equilibrated Structures: Sequential Lattice Oxygen Evolution Shapes Mars–van Krevelen Catalytic Oxidation on β-MnO₂(110)

Abstract

Catalytic oxidation on a large number of reducible transition metal oxides can be described by the Mars–van Krevelen (MvK) mechanism, wherein the redox behavior of lattice oxygen (O lat ) plays a central role. As a result, the formation energy ( E vac ) of the oxygen vacancy (O V ), typically derived from a stoichiometric or thermodynamically equilibrated surface, is widely used as a descriptor of the catalytic activity. However, this approach overlooks the dynamic evolution of the surface due to the continuous consumption of O lat during the reaction. In this work, using CO oxidation on β-MnO 2 (110) as a probe, we combine density functional theory and kinetic Monte Carlo simulations to demonstrate the importance of sequential consumption and regeneration of O lat in dictating catalytic performance. We find that E vac is not static but varies with O V concentration, altering the equilibrium between O lat reduction and regeneration. As the accumulation of O V shifts the reaction mechanism from being reduction-dominated to regeneration-dominated, the steady-state surface composition deviates significantly from the prediction based on the thermodynamic equilibrium model. Only by accounting for the dynamic variation of O lat can the simulated apparent activation energies and reaction orders be closely reconciled with experimental observations. This work challenges the traditional reliance on the initial E vac and offers a more accurate portrayal of catalytic oxidation within the MvK mechanism, which provides useful guidance for predicting and optimizing catalytic activity toward real-world applications.

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