Modelling of the Gibbs adsorption at transition-metal–oxide interfaces: effect of the oxygen chemical potential on interfacial bonding, interfacial energy and equilibrium precipitate shape

Abstract

Abstract Non-reactive ternary metal–oxide interfaces are thermodynamically stable over extended ranges of oxygen activities and temperatures. At each condition within this range, the interface adopts a different equilibrium structure and chemistry. A continuum model of the Gibbs adsorption–desorption at transition-metal–oxide interfaces is developed, which predicts interfacial chemistry and modifications in the specific free interfacial energy as a function of oxygen activity. Three oxygen activity domains can be distinguished according to this model: the upper part of the metal–oxide coexistence range characterized by an enrichment in interfacial oxygen, established by adsorption of oxygen at structural vacancies in the case of polar interfaces or by desorption of the less noble metal in the case of mixed interfaces; an intermediate-oxygen-activity range with the interface remaining free of adsorption; a lower-oxygen-activity range, where the interface is enriched in less noble metal by adsorption of exc...