Design of materials for solid oxide fuel cells cathodes and oxygen separation membranes based on fundamental studies of their oxygen mobility and surface reactivity

¹ Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Russia
² Novosibirsk State University, 630090, Novosibirsk, Russia
³ Institute of High Temperature Electrochemistry UB RAS, 620137 Yekaterinburg, Russia
⁴ Ural Federal University, 620002 Yekaterinburg, Russia

^* Corresponding author: sadykov@catalysis.ru

Abstract

Design of materials for solid oxide fuel cells cathodes and oxygen separation membranes and studying their oxygen transport characteristics are important problems of modern hydrogen energy. In the current work, fundamentals of such materials design based on characterization of their oxygen mobility by oxygen isotope exchange with C¹⁸O₂ and ¹⁸O₂ in flow and closed reactors for samples of Ruddlesden – Popper-type oxides Ln_2-xCa_xNiO_4+δ, perovskite-fluorite nanocomposites PrNi_0.5Co_0.5O_3-δ – Ce_0.9Y_0.1O_2-δ, etc. are presented. Fast oxygen transport was demonstrated for PNC – YDC (DO ~10^-8 cm²/s at 700°C) nanocomposites due to domination of the fast diffusion channel involving oxygen of the fluorite phase with incorporated Pr cations and developed perovskite-fluorite interfaces. For LnCNO materials a high oxygen mobility (DO ~10^-7 cm²/s at 700°C) provided by the cooperative mechanism of its migration was demonstrated. Depending on Ca dopant content and Ln cation nature, in some cases 1–2 additional channels of the slow diffusion appear due to decreasing the interstitial oxygen content and increasing the energy barrier for oxygen jumps due to cationic size effect. Optimized by the chemical composition and nanodomain structure materials of these types demonstrated a high performance as SOFC cathodes and functional layers in asymmetric supported oxygen separation membranes.