Introducing Ag in Ba0.9La0.1FeO3-δ: Combining cationic substitution with metal particle decoration

Abstract

BaFeO3−δ-derived perovskites are promising cathodes for intermediate temperature solid oxide fuel cells. The activity of these perovskites depends on the number of oxygen vacancies in their lattice, which can be tuned by cationic substitution. Our first-principle calculations show that Ag is a promising substitute for the Fe site, resulting in a reduced oxygen vacancy formation energy compared with the pristine BaFeO3−δ. Ag has limited solubility in perovskites, and its introduction generates an Ag metal secondary phase, which influences the cathode performances. In this work, we investigate the matter, using a Ba0.9La0.1Fe1−xAgxO3−δ series of materials as a case study. Acknowledging the limited solubility of Ag in Ba0.9La0.1Fe1−xAgxO3−δ, we aim to distinguish the effects of Ag substitution from those of the Ag secondary phase. We observed that Ag substitution increases the number of oxygen vacancies, confirming our calculations, and facilitates the oxygen incorporation. However, Ag substitution lowers the number of holes, in this way reducing the electronic p-type conductivity. On the other hand, Ag metal positively affects the electronic conductivity and helps the redistribution of the electronic charge at the cathode-electrolyte interface.

Keywords

• Solid oxide fuel cells
• Mixed ionic electronic conductors
• Ag substitution
• Ag particles decoration
• BaFeO3-δ-derived perovskites