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In this work, we performed DFT+U periodic calculations to study the geometric and electronic properties of 12.5% Mn-doped CeO2 solid solution. The doping with Mn allowed some Mn2+ cations to substitute Ce4+ ions into the CeO2 lattice and thus drove the formation of a stable O-deficient bulk fluorite-type structure. The Mn-doped CeO2(1 1 1) surface, generated upon the cleavage of the O-deficient bulk, exhibits Mn cations in a (3+) oxidation state. Spin-polarized energy calculations and charge analysis also evidenced the effect of Mn-dopant in facilitating the creation of surface oxygen vacancies; which reflected in extended surface and subsurface ions relaxation and reduction of Mn atoms located on surface and inner cationic layers. Concerning the oxidation state of Ce, it remained unaltered as Ce4+ when an O atom was removed from the topmost anionic layer of the surface system. Reduction of a Ce4+ cation to Ce3+ was evidenced after the creation of a second surface O-vacancy. Our results indicate facilitated surface oxygen release, Mn3+/Mn2+ redox couples formation, and promoted anionic mobility and can help to better understand the effect of Mn in enhancing Mn-doped CeO2 catalytic performance in oxidation reactions.

We performed DFT+U quantum period calculations to study the characteristics of Ni interactions on/in CeO2−ZrO2 mixed oxide solid solutions. We analyzed the energetics of Ni adsorption and insertion on/in different surface and subsurface sites of the Ce0.25Zr0.75O2(111) slab, and also the changes in its atomic and electronic structures. The most stable interaction corresponds to a single Ni atom adsorbed on the O−O bridge site, where the nearest-neighbor metal atom is the Zr. Our calculations also show that Ni can form small clusters on the Ce0.75Zr0.25O2(111) surface; which also locate around the Zr dopant. Due to Ni interactions, surface and inner layers oxygen anions experience important modifications in their geometric positions and the Ni atom deposition results in the partial occupation of 7-coordinated Ce(4f) states.

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