Ceria can serve as an active support for transition metal catalysts, and numerous studies indicate that the interface between ceria and supported transition metals exposes unique chemical functionality.  Many transition metals will mix with ceria to form a mixed oxide system, and these systems also exhibit unique desulfurization and hydrocarbon oxidation activity.  The activity of these systems is linked to the redox properties of the M/CeO2 system.  Density functional theory has been applied to examine ceria based systems, however, the well-known difficulties for DFT to represent the localized f-electrons in reduced ceria calls into question catalytic reaction energetics derived from DFT methods.  The addition of an empirical correction on the localized f-electron states through the DFT+U method can provide reasonable electronic structure behavior, however, the reliability of DFT+U methods to examine M-doped systems is not well established.  As DFT also fails to accurately represent localized d-electrons on transition metal oxides, the application of DFT+U methods to the M/CeO2 system introduces additional questions as to the reliability of mixing empirical U corrections for both Ce f-states and M d-states.  In this talk, examples of the electronic structure impact of U corrections for M-doped CeO2 surfaces will be demonstrated and the impact of these corrections on catalytic properties will be discussed.  Mn- and Pd-doped systems will receive special attention due to their demonstrated activity for desulfurization and hydrocarbon oxidation.  Comparisons with hybrid functional calculations and experimental XANES studies of the Mn/CeO2 system will demonstrate that qualitatively reliable behavior can be obtained by using U corrections derived to replicate properties of the component bulk oxides.

Density functional theory methods for examining active sites of M-doped ceria surfaces

246th National Meeting (2013)

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