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

Abstract

The proton uptake behavior of the BaySr_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‑δcomposition (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 ΔG_hyd^O reported for the BaySr_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.