Reaction mechanism between small-sized Ce clusters and water molecules II: an ab initio investigation on Ce (n = 1-3) + mHO (m = 2-6).

Possible reactions between the products of the three independent reactions involving a small Ce cluster and a single water molecule, Cen + H2O (n = 1-3), and an additional H2O molecule are systematically investigated. The ground-state isomers of the final products and the reaction pathways involving multiple water molecules are predicted. We find that under either ambient or UV-irradiation conditions, all the reactions can entail low energy barriers. In addition, the final products of the reaction between Cen and more than two H2O molecules are also predicted through an extensive structural search. The calculated reaction energies suggest that although small-sized Ce clusters can react with more than two water molecules, the reactions with one or two water molecules are dominant. The electronic structures of all the ground-state isomers and the corresponding oxidation states of Ce atoms in these isomers are computed and determined via the natural bond orbital (NBO) method. The results indicate that a single Ce atom and a Ce2 cluster can react with a maximum of four and six water molecules, respectively, while a Ce3 cluster can react with more than six water molecules. This comprehensive study offers an improved understanding of the mechanism underlying the reactions between a single Ce atom or a small Ce cluster and two or more H2O molecules. Knowledge obtained from this study can be helpful for the development of high-performance Ce-doped or Ce-based catalysts.