1. Department for Hydrogen Technology, Institute for Energy Technology, P.O. Box 40, NO-2027, Kjeller, Norway
2. Department of Mathematics and Physics, University of Stavanger, P.O. Box 8600, NO-4036 Forus, Norway
3. Department of Science and High Technology and INSTM, Università degli Studi dell’Insubria, Via Valleggio 9, I-22100 Como, Italy