H2 Dissociation and Oxygen Vacancy Formation on Ce2O3 Surfaces

H2 dissociation on ceria (CeO2) has attracted much attention in the last years because of its potential application in catalysis for hydrogenation reactions, as well as for the stabilization of hydride bulk and surface species. The ability of ceria to split hydrogen is strongly dependent on the surface morphology. However, to the best of our knowledge, the reactivity of the cerium sesquioxide Ce2O3 A-type (hexagonal structure with space group P3¯m1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P\bar{3}m1$$\end{document}) has not been previously addressed. In the present study, we investigate (i) the formation of oxygen vacancies in A-Ce2O3 bulk and (ii) the effect of the surface topology in the H2 dissociation and in the oxygen vacancy formation for the four most stable surfaces of A-Ce2O3: (0001), (01− 11), (11− 20) and (11− 21). Our results indicate a significant decrease of the energetic barrier for the hydrogen dissociation compared to stoichiometric CeO2, with an activation energy of ~ 0.1 eV. Interestingly, Ce2O3 surfaces lead to a heterolytic product with hydride species more stable than the homolytic product, which is the opposite behavior found in CeO2. These results suggest a better performance of Ce2O3 than CeO2 for H2 dissociation and provide insight in the nature of hydride-Ce2O3 interfaces that could be important intermediates in the formation of CeHx phases from cerium oxide.