In the case of water electrolysis wet hydrogen is produced, which has to be dried before storing. Cost-efficient and highly selective membranes might have the potential to separate the water effectively with low parasitic energy demand. The main objective is to coat a stable polymer carrier structure, which is highly permeable for hydrogen, with an ultra thin metallic layer in a range of several nano meter thickness. The resulting composite membranes should be tight for water but highly permeable for hydrogen. Based on generated experimental data a technical and economical assessment will be made.
The project started in February 2013 and can be divided into three time spans. First the development of suitable polymer carrier structures, the advancement of a coating technology for generation of ultra thin layers and the setup of a test arrangement for characterisation and assessment of the later on prepared membranes will be performed in parallel. After about one year when the coating method has been established and the uncoated polymer carriers have been characterised first tests with metal coated composite membranes will be performed. These experiments as well as the further development of polymer carriers and metal coatings will last for the whole project duration. After two years suitable results should be available in order to prepare some concept designs for a drying unit and to make an economic assessment in comparison to existing drying techniques.
New gas separation membranes
The main focus of the project is on the research and development of new gas separation membranes. These consist of an ultra thin metallic layer, which is responsible for the functionality, and a polymer substrate. That carrier has to be optimised with respect to surface structure in order to allow defect-free coating by a metal deposition process. On the other side it should be as open as possible so that the dry hydrogen flow is unhindered. Additional the system has to be mechanical stable to withstand the occurring differential pressure forces between feed and permeate side of the membrane. Beside material and structure of the polymer carrier the choice of metallic alloys and the coating procedure are of fundamental relevance. Adhesion, uniformity and stability of the coating can be influenced by the deposition process and its operating parameters. These interdependencies will be investigated in the project.
Optimising structure and material properties
Hydrogen as energy carrier can be used to store surplus energy from renewable sources by means of water electrolysis. The so generated hydrogen has to be dried before it can be stored and than can be used to produce electricity on demand or as feedstock e.g. for passenger cars, busses or material handling systems. Drying procedures like pressure swing adsorption (PSA) or temperature swing adsorption (TSA) are realised in industrial scale but need for continuous operation several reactors, which alternately dry the gas and being regenerated, respectively. Based on preliminary work BASF SE will develop polymer carriers which are optimised with respect to structure and material properties. The work group of Prof. Buck at University Duisburg-Essen uses these polymer membranes as substrate for ultra thin metallic layers, consisting of different Palladium-Silver alloys. The resulting gas separation membranes has to be tested and characterised at Zentrum für Brennstoffzellentechnik.