1. Department of Materials Science and Engineering, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway
2. Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
3. Surface Science Laboratory, Department of Materials- and Earth Sciences, Technical University Darmstadt, Otto-Berndt-Str. 3, 64287 Darmstadt, Germany
4. Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany