investigation of the formation of ZrO-like structures upon the adsorption of Zr on the CeO(111) surface.

The adsorption of Zr on the CeO surfaces can lead to the formation of ZrO-like structures, which can play a crucial role in the catalytic properties of Ce Zr O as support for transition-metal catalysts; however, our atomistic understanding is far from satisfactory, and hence, it affects our capacity to engineer the combination of ZrO-CeO for catalysis applications. Here, we investigate the adsorption of Zr ( = 1 - 4) atoms on CeO(111) surfaces through density functional theory with the Hubbard model and bring new insights into the Zr-CeO interaction and the formation of ZrO-like structures on ceria. We found that the Zr atoms oxidize to Zr and strongly interact with the O anions, reducing the surface Ce cations to Ce (4 Ce atoms per Zr adatom), which stabilizes the system by more than 10 eV per Zr. As more Zr is adsorbed, the O species migrate from the sub-surface to interact with the on-surface Zr adatoms in hcp sites, producing a full ZrO-like monolayer, which contributes to reduce the strain induced by the increased size of the Ce cations compared with Ce. The simulated partial and full ZrO-like structure thicknesses agree with the experimental measurements. In addition, we found an unprecedented trend for the on-surface Zr atoms: our calculations show that they are less stable than Zr replacing Ce atoms from the first cation layer. Therefore, under sufficiently high temperatures, one expects the formation of a CeO-like/-ZrO/CeO structure, which may completely change the reactivity of the surface.