of mixed ionic-electronic conducting oxides
High-temperature electrochemical devices such as solid oxide fuel cells, solid oxide electrolysis cells, oxygen separation membranes and membrane reactors based upon fast oxygen ionic conducting oxides have the potential to provide great economic and ecological benefits. One of the challenges of researchers in this field is to develop materials showing fast oxygen ionic transport and fast surface exchange kinetics under given operating conditions. It is therefore important to gain a fundamental understanding of the factors controlling oxygen surface exchange, such as defect chemistry and defect-related properties, degree of oxygen non-stoichiometry, surface composition and grain boundary properties.
Main characterization techniques used to determine the oxygen surface exchange kinetics of fast ionic conducting oxides include 18O-16O isotopic exchange depth profiling method (IEDP), 18O-16O isotopic exchange gas phase analysis (IE-GPA), 18O-16O isotopic exchange pulse technique (PIE), electrical conductivity relaxation (ECR), electrochemical impedance spectroscopy under controlled atmosphere (humidity and pO2). Data from, e.g., low energy ion scattering (LEIS) and X-ray photo electron spectroscopy (XPS) is used to relate the observed oxygen exchange kinetics to the surface and near-surface composition of the materials.
Major aim of my lecture is to present recent progress and challenges of studies towards understanding the oxygen surface exchange kinetics of single-phase and composite mixed ionic-electronic conducting oxides.
