1. Physics Department, Institute for Energy Technology, P.O. Box 40, NO-2027,
Kjeller, Norway
2. Division of Hydrogen & Energy, Department of Mobil Environment & Energy, Empa Materials Science & Technology, Uberlandstrasse 129, CH-8600 Dubendorf, Switzerland
3. Institute
of Nanotechnology, Karlsruhe Institute of Technology, POB 3640, D-76021
Karlsruhe, Germany