Understanding and identifying the oxygen transport mechanisms through a mixed-conductor membrane

•Impact of temperature, pO2 and microstructure on oxygen permeation flux and rate determining step.•Mapping of mixed conductors with surface exchange coefficient and ionic conductivity.•Understanding of oxygen transport mechanisms through the membranes.•Improving the surface exchange by ultra-divided particles.•Optimal design membranes with specific microstructures. Recent developments in oxygen transport membranes have led to a selection of membrane materials or designs to achieve a judicious compromise between the oxygen flux, chemical stability and mechanical performance of membranes under operating conditions. This paper briefly describes the state of the art in the current understanding of oxygen transport through mixed-conductor membranes for oxygen separation. A better understanding of oxygen transport mechanisms, in particular, oxygen exchange at the membrane surface, leads to the identification of relevant key parameters that control the oxygen semi-permeation performance of the membrane. From a rational approach, key parameters are identified and discussed to identify promising membrane materials.