[1] Tech Univ Denmark, Surface Phys & Catalysis SurfCat, Dept Phys, Fysikvej B311, DK-2800 Lyngby, Denmark
[2] Tech Univ Denmark, Dept Micro & Nanotechnol, Orsteds Plads B344, DK-2800 Lyngby, Denmark
[3] Delft Univ Technol, MECS, Dept Chem Engn, Delft, Netherlands