(284f) Computational Characterization of Pd/Ceria Catalysts Using DFT+U and ReaxFF

Catalyst design plays an indispensible role in optimizing processes to meet ever rising demands for efficient and clean energy technologies. Numerous experimental studies have demonstrated the high activity of ceria supported palladium catalysts. Pd/ceria catalysts have the potential for application in catalytic combustion, as automotive three-way catalysts, and as solid-oxide fuel cell (SOFC) anodes.  To fully realize this potential, we must determine the nature of active sites on the Pd/ceria interface. In this study, multi-scale computational techniques are used to characterize the structure, stability, and reactivity of the Pd/ceria surface. Density functional theory including on site Coulombic interaction (DFT+U) provides quantum mechanical data describing the energetics of Pd/ceria interactions and hydrocarbon activation over the Pd/ceria surface. The data obtained from DFT+U calculations are used to parameterize a reactive force-field (ReaxFF) capable of describing larger length and time scales via Monte Carlo (MC) and reactive molecular dynamic (RMD) simulations. RMD simulations allow this study to investigate aspects of the system that are computationally intractable for ab initio methods, such as the dyanmic restructuring of the catalyst surface during reaction.  Initial DFT+U results demonstrate that a single Pd atom incorporated into the CeO₂(111) surface significantly lowers the reaction barrier for methane C-H bond activation compared to pure CeO₂(111). Furthermore, ab initio thermodynamic approaches indicate that the Pd_incorporated structure is stable under high oxygen partial pressures and low temperatures (~5 atm, 250 K).