1. Institute of Hydrogen Technology, Helmholtz-Zentrum Hereon, Max-Planck-Straße 1, Geesthacht 21502, Germany
2. Laboratory for Energy Applications for the Future (LEAF), Lawrence Livermore National Laboratory, Livermore, California 94550, USA
3. Institute of Materials Technology, Helmut-Schmidt-University, Holstenhofweg 85, Hamburg 22043, Germany