Article

Entropic contributions enhance polarity compensation for CeO2(100) surfaces

  • Nature Materials volume 16, pages 328334 (2017)
  • doi:10.1038/nmat4804
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Abstract

Surface structure controls the physical and chemical response of materials. Surface polar terminations are appealing because of their unusual properties but they are intrinsically unstable. Several mechanisms, namely metallization, adsorption, and ordered reconstructions, can remove thermodynamic penalties rendering polar surfaces partially stable. Here, for CeO2(100), we report a complementary stabilization mechanism based on surface disorder that has been unravelled through theoretical simulations that: account for surface energies and configurational entropies; show the importance of the ion distribution degeneracy; and identify low diffusion barriers between conformations that ensure equilibration. Disordered configurations in oxides might also be further stabilized by preferential adsorption of water. The entropic stabilization term will appear for surfaces with a high number of empty sites, typically achieved when removing part of the ions in a polar termination to make the layer charge zero. Assessing the impact of surface disorder when establishing new structure–activity relationships remains a challenge.

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Acknowledgements

This research has been supported by the ERC Starting Grant and Proof of Concepts (ERC-2010-StG-258406, ERC-2015-PoC_680900), the Ministerio de Economía y Competitividad—MINECO (CTQ2015-68770-R), and the Generalitat de Catalunya—AGAUR (SGR-2014-SGR-145). M.C.-C. acknowledges MINECO for a ‘Juan de la Cierva—Formación’ fellowship (FJCI-2014-20568). We acknowledge BSC-RES and CSUC for providing generous computational resources. We thank R. Grau-Crespo (University of Reading) for kindly providing us with the SOD software and A. Selloni (Princeton University) for critically reading the manuscript.

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Affiliations

  1. Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain

    • Marçal Capdevila-Cortada
    •  & Núria López

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Contributions

M.C.-C. performed the calculations. M.C.-C. and N.L. analysed the data and prepared the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Marçal Capdevila-Cortada or Núria López.

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