Rian Ruhl is a PhD candidate at the University of Twente since March '14. His research is part of the GREEN-CC FP7 European project and focuses on the development and optimization of membrane materials for separating oxygen out of air. These materials are so-called Mixed Ionic and Electronic Conductors (MIECs): materials capable to transport oxygen ions through dense structures. When operated at temperatures in the range of 600 - 900 °C, oxygen can be purified with 100% selectivity. The challenge of the work is to develop membrane materials that allow for a high oxygen flux, while retaining their chemical and mechanical integrity. Experiments at the UT focus on electrochemical characterization of the materials to increase the understanding of transport properties.