| Sumario: | In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO 2 (111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce 0.963 Pr 0.037 O 2 (111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr 3+ and Ce 3+ ones. Praseodymium doping also favors the activation of O 2 molecule on surface O-holes, leading to formation of a superoxide (O 2 − ) radical as well as to reoxidation of the Ce 3+ cation to Ce 4+ one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO 2 molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO 2 solids. © 2016 Elsevier B.V.
|
|---|