Charge localization in doped and undoped ceria: the non-standard model

ANA MARÍA LLOIS; VALERIA FERRARI; VERÓNICA VILDOSOLA; GUSTAVO MURGIDA

Zaragoza

Congreso; CECAM Workshop in Zaragoza; 2011

p { margin-bottom: 0in; text-align: justify; }p.western { } The role played by ceria in catalytic applications is well known and it is widely recognized that it is of outmost importance to study its capability for oxygen storage as well as the possibility of reversible oxygen release [1]. There is experimental evidence supporting the idea that excess electrons left behind by oxygen vacancies localize in specific Cerium atoms in the case of pure ceria, and in Cerium as well as in dopant atoms in the case of doped ceria. The location of the reduced Ce atoms, that is of the localization of the excess electrons, paves the way to understand catalytic processes in ceria based systems as well as magnetic properties in the case of doping. According to the standard model (SM), in reduced bulk ceria, charge localization takes place at Ce sites nearest neighbors of oxygen vacancies [2]. Recently, this SM view has been challenged by calculations done for, both, the bulk [3] and the reduced CeO2 (111) surface [4,5]. In this talk we are going to report about the studies undertaken to test the validity of the standard model versus, what we call, the non standard model (NSM), for partially reduced ceria and reduced ceria doped with magnetic impurities, in particular Co. We focus on the location of vacancies along with charge localization on the cooresponding Ce atoms. The computational approach used to face the problem will be presented along with the historical path gone through, since we started to tackle this system.