**Acknowledgements**

The authors acknowledge fruitful collaboration, extensive test work and the positive relationship to Technical University of Clausthal, German Aerospace Center Oldenburg (Institute of Networked Energy Systems) and Research Center of Fuel Cell Technology (ZBT) in Duisburg.

Public funding is gratefully acknowledged from Federal Ministry for Economic Affairs and Energy (Germany) and Ministry of Education and Research (Germany) in cooperation with the project holder Forschungszentrum Jülich in the projects 'Redox Flow Extrusion', 'Re3dox', 'Demo-Bio BZ' and from the State of Lower Saxony in the project "Maleskues" and "Titan Porous Hybrid".
