We combine density functional theory (DFT) and reactive force-field (ReaxFF) simulations to assess the stability and activity of unique catalytic sites at the interface between Pd clusters and a CeO2 support. ReaxFF-based Grand Canonical Monte Carlo (GC-MC) simulations provide insight into the oxide structure at the Pd/CeO2 interface. Surface models derived with GC-MC are employed in reactive molecular dynamics (RMD) simulations, which demonstrate that methane lightoff rapidly occurs when there is Pd mixing in the CeO2 lattice. DFT investigations, utilizing models inspired by GC-MC/RMD, demonstrate that Pd4+ states are stabilized in PdOx clusters partially embedded in the CeO2 lattice, and that such sites yield low methane activation barriers. The integrated DFT/ReaxFF methodology employed here demonstrates a combined quantum/classical workflow that can be extended to examine emergent behavior in other oxide-supported metal catalysts. (Chemical Equation Presented).
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