Abstract
The effect of U cations on the reduction of CeO2 is studied by modeling the Ce1-xUxO2 systems with density functional theory (DFT) at the GGA + U (U = 5.0 eV) level of theory. Oxygen-vacancy formation energies (E-Ovac) are influenced by substituting Ce4+ cations in CeO2 by U4+ cations. The pDOS analyses indicate charge transfer mechanism from the O2p and U5f orbitals to the Ce4f orbitals upon the creation of an oxygen vacancy resulting in the reduction of three Ce4+ cations (instead of two in the un-doped system) to three Ce3+ cations. A linear correlation between E-Ovac and U content has been found which may explain the initially observed experimental correlation between H-2 production from water on this system. The increased hydrogen production from water using mixed charged elements (such as Ce and U in this work) may be rationally designed computationally.