Methane Combustion Mechanisms on Ni₁₀/CeO₂ Studied by DFT, Microkinetic Modeling, and Kinetic Monte Carlo Simulation

Methane combustion mechanisms on Ni₁₀/CeO₂ have been studied by using density functional theory (DFT). The results show that the cleavage of the first C–H bond of CH₄ occurs on the top Ni sites without the assistance of the lattice oxygen or the adsorbed oxygen. Then CH_x (x = 1, 2, 3) species dehydrogenate continuously until C, while CH_x oxidation needs higher activation energy. The H₂O formation mainly proceeds via the lattice oxygen mechanism. To understand the reaction mechanisms under experimental conditions, both mean-field microkinetic modeling (MF-MKM) and kinetic Monte Carlo (KMC) simulations are employed. The simulation results indicate that the lattice oxygen plays an important role in the CO₂ and H₂O formation steps, and CH_x direct dissociation dominates the pathway instead of CH_x oxidation, which can support the DFT results. Moreover, the oxygen coverage of KMC simulations is much lower than that of MF-MKM containing the O–O interaction, and the reaction order data obtained by KMC are closer to the experimental results, indicating KMC simulations can better describe adsorbate lateral interactions and spatial correlations.