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

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 (Olat) plays a central role. As a result, the formation energy (Evac) of the oxygen vacancy (OV), 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 Olat during the reaction. In this work, using CO oxidation on β-MnO2(110) as a probe, we combine density functional theory and kinetic Monte Carlo simulations to demonstrate the importance of sequential consumption and regeneration of Olat in dictating catalytic performance. We find that Evac is not static but varies with OV concentration, altering the equilibrium between Olat reduction and regeneration. As the accumulation of OV 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 Olat can the simulated apparent activation energies and reaction orders be closely reconciled with experimental observations. This work challenges the traditional reliance on the initial Evac 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.