Enhanced proton uptake in triple-conducting BaySr1−y(Fe0.75Mo0.25)1−2xZnxZrxO3−δ perovskites

Abstract

The proton uptake behavior of the Ba_ySr_1−y(Fe_0.75Mo_0.25)_1−2xZn_xZr_xO_3−δ materials intended for application in solid oxide and protonic ceramic fuel and electrolysis cells (SOFCs/SOECs, PCFCs/PCECs) is extensively studied to elucidate the role of Ba, Zr, and Zn dopants in the formation and stabilization of protonic defects. Compared with the parent SrFe_0.75Mo_0.25O_3−δ composition (SFM), the modified compounds exhibit a pronounced enhancement in terms of proton uptake capabilities, with proton concentration at 250 °C changing from 0.05% for the base SFM to 9.0% for the modified BaFe_0.45Mo_0.15Zn_0.2Zr_0.2O_3−δ material. The analysis shows that the main driving factors for this behavior are increased oxygen non-stoichiometry associated with Zn incorporation, together with lattice expansion and increased overall basicity induced by Ba substitution. The values of reported for the Ba_ySr_1−y(Fe_0.75Mo_0.25)_1−2xZn_xZr_xO_3−δ series show a strong correlation with fundamental properties, such as electronegativity and total electrical conductivity, as has been reported for other triple-conducting perovskites. Overall, the study explores the extent of possible modifications for the highly-coveted SFM-based compounds, at the same time providing a much-needed insight into the design principles of effective triple-conducting materials, essential for the further development of the PCFC technology.