The effect of defect interactions on the reduction of doped ceria

Abstract

Doped cerium oxide is known for its reduction properties that are utilized in catalytic applications as well as in thermochemical cycling to produce solar fuels. Upon reduction of the lattice, oxygen vacancies and polarons are formed leading to a highly concentrated solution of defects in which the interactions of defects cannot be neglected anymore. In this study, the effect of defect interactions on the free energy of reduction for doped ceria with composition Ce_1−x−yRE_xZr_yO_2−x/2−δ was investigated by large scale Metropolis Monte Carlo multi-stage sampling simulations based on first-principles calculations. The simulations allowed the prediction of the relation between oxygen partial pressure and non-stoichiometry for the highly interacting, non-ideal system. The results show that the non-ideality observed in experiments can be traced back to the interactions of defects and allow prediction of the reduction behavior for various dopant types, dopant fractions, temperatures, and non-stoichiometries.