O vacancies on steps on the CeO2(111) surface

Cerium dioxide is a compound important for heterogeneous catalysis, energy technologies, biomedical applications, etc. One of its most remarkable properties is low O vacancy (O-vac) formation energy E-f. Nanostructuring of ceria was shown to decrease E-f and to make the oxide material more active in oxidative reactions. Here we investigate computationally formation of O-vac on CeO2(111) surfaces nanostructured by steps with experimentally observed structures. To facilitate the search for O-vac + 2Ce(3+) configurations that yield the lowest E-f values we proposed and employed an efficient computational scheme where DFT + U calculations were preceded by a pre-screening procedure based on the results of plain DFT calculations. E-f values on the steps were calculated to be up to 0.7 eV lower than on a regular CeO2(111) surface. Some energetically stable O-vac + 2Ce(3+) configurations were found to include subsurface Ce3+ ions. The present results quantify to what extent the roughness of the CeO2(111) surface affects its reducibility.