Fluorine impurities at CeO2(111) : Effects on oxygen vacancy formation, molecular adsorption, and surface re-oxidation

• We investigate the effects of anion doping with fluorine impurities on the chemistry of the CeO2 (111) facet, using the results of DFT+U calculations. We consider three prototypical processes: the formation of oxygen vacancies, the adsorption of O-2 and H2O molecules, and the re-oxidation of the surface with fragments of the two molecules. We find that the first two of these processes are not strongly affected, but that the presence of F lowers the energy gained in the re-oxidation of the surface in comparison to the healing of an oxygen vacancy, by 1.47 eV in the case of O-2 (provided that the F is part of a cluster) and by 0.92 eV in the case of H2O. Based on these results, we suggest that F could enhance the redox chemistry of ceria by toggling between being in the surface and on the surface, effectively facilitating the release of lattice O by acting as a "place holder" for it. Finally, we find that the desorption of F as either 1/2 F-2 or HF is energetically unfavourable, suggesting that F doped ceria should be stable in the presence of O-2 and H2O.

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NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

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