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Structure and Electronic Properties of [Ca₂₄Al₂₈O₆₄]⁴⁺·4e– Surfaces: Opportunities for Termination-Controlled Electron Transfer

Ong, Phuong-Vu, Hosono, Hideo, Sushko, Peter V.
Journal of physical chemistry 2019 v.123 no.10 pp. 6030-6036
adsorption, aluminum oxide, anions, calcium oxide, catalysts, density functional theory, electron transfer, gold, thermodynamics
We investigate the structure, thermodynamic stability, and electronic properties of (001), (110), and (111) surfaces of mayenite (12CaO·7Al₂O₃ or C12A7) in its oxygen-deficient phase known as mayenite-derived electride Ca₁₂Al₁₄O₃₂ using simulations based on the density functional theory. Seven types of surface terminations were identified, depending on the orientation of the lattice nanosize cages with respect to the surface plane. We find that the surface termination has a strong effect on the distribution of electron anions in the near-surface region, as demonstrated by the range of the ionic charges and binding energies of adsorbed Au atoms and dimers. Notably, in all cases, Au species acquire a negative charge and preferentially adsorb as isolated ions rather than aggregate into clusters. These results show that C12A7 electride can provide a simple, yet versatile substrate to achieve high adsorption capacity and steric selectivity for single atom catalysts.