Reduction Process in CeO₂−MO and CeO₂−M₂O₃ Mixed Oxides:  A Computer Simulation Study

A computer simulation study of the Ce 4+ /Ce 3+ reduction process in CeO 2 −MO (M = Ca, Mn, Ni, Zn) and CeO 2 −M 2 O 3 (M = Sc, Mn, Y, Gd, La) mixed oxides is presented. Calculations satisfactorily reproduce the observed structural parameters of the solid solutions over a wide range of compositions. On energetic grounds, the Ce 4+ /Ce 3+ reduction process is enhanced with increasing dopant content, with the enhancement being more pronounced for divalent dopants. For a fixed dopant level, the reduction of cerium is more favorable for larger dopant ions. The results are explained in terms of the higher oxygen vacancy concentration and the larger dopant size being effective in accommodating the greater relaxation or elastic strain associated with forming the larger Ce 3+ species upon reduction.