Quantitative characterization of Cr-adsorption on CeO₂, pure and doped BaCeO₃ and its impact on the electrochemical performance of Ce containing complex oxides

Quantitative analysis of Cr-adsorption from a gas phase on CeO₂, pure and doped BaCeO₃ was performed in combination with surface techniques and electrochemical impedance spectroscopy. The Cr-adsorption on BaCeO₃ is 3 times higher than on CeO₂ and it increases by 12–25% on In doping in Ba(Ce_1−xIn_x)O₃ (x = 0.1–0.3) in the temperature range of 600–700 °C. These perovskites adsorb chromium with the formation of a multi-phase surface layer containing BaCr⁶⁺O₄ and cerium oxide. Coexistence of small fractions of Cr³⁺ and Cr⁵⁺ cations in the surface layer was identified by X-ray photoelectron spectroscopy. The thickness of the surface layer and its morphology vary with temperature, affecting the conductivity of Ce containing perovskites below 700 °C. BaCrO₄ exhibits under air noticeably larger anisotropic thermal expansion than BaCeO₃. The results indicate that high tolerance to Cr-gaseous species should be considered as an important criterion for further development of materials for proton-conducting SOFCs.