1. Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland, Empa, Swiss Federal Laboratories for Materials Testing and Research, Hydrogen & Energy, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland, and ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, U.K.