[1] Univ Duisburg Essen, Fac Phys & CENIDE, Carl Benz Str 199, D-47057 Duisburg, Germany
[2] ZBT GmbH, Hydrogen & Fuel Cell Ctr, Carl Benz Str 201, D-47057 Duisburg, Germany
[3] Univ Duisburg Essen, Interdisciplinary Ctr Analyt Nanoscale, Lotharstr 1, D-47057 Duisburg, Germany
[4] Univ Duisburg Essen, Fac Chem & CENIDE, Univ Str 5-7, D-45141 Essen, Germany