Direct membrane deposition: Proof of concept for AEM electrolysis

Bastian Kaufmann, The hydrogen and fuel cell center (ZBT GmbH), Duisburg, Germany
Miriam Hesse, The hydrogen and fuel cell center (ZBT GmbH), Duisburg,
Moritz Pilaski, The hydrogen and fuel cell center (ZBT GmbH), Duisburg,
Harry Hoster, University of Duisburg-Essen, Lehrstuhl Energietechnik, Duisburg,

Alkaline membrane water electrolysis (AEM-WE) gained increasing attention in the last couple of years. This can mainly be attributed to the improvements in ionic conductivity of the alkaline exchange membrane (AEM) materials, which now rivals the ionic conductivity of the ever-present PEM materials (e.g. Nafion™) under comparable acidic conditions. The inherent advantage of AEM-WE is, due to the alkaline media, the lack of dependence on platinum group metal catalysts, such as iridium. Therefore, investment costs could be lowered and sustainability improved. Here we employ direct membrane deposition (DMD) as a novel membrane electrode assembly (MEA) fabrication technique. DMD has been thoroughly studied by Breitwieser et. al. in PEM fuel cells [1,2]. We present the first reported DMD-MEA for AEM-WE. To investigate the influence of DMD on MEA performance we have fabricated several MEAs with five commercially available AEM ionomers via ultra sonic spray coating. These ionomers were directly coated onto the anode and cathode respectively, and a gasket was sandwiched between the half-MEAs, which were subsequently pressed together to form one continous membrane. These DMD-MEA were in-situ electrochemically investigated (polarization curve, EIS) and compared to their respective MEA with casted membrane. To further study the morphological structure of the DMD-MEAs SEM images of the cross-sections were taken. It could be observed, that the rough surface area of the used stainless steel felts, first thought to be a main obstacle, did not hinder a continuous membrane formation and did not lead to electrical shorting. Furthermore, we can report an increased current density for the DMD-MEA which can be attributed to lowered charge transfer resistances (Rct). This is slightly remarkable since the Rct is mostly governed by the catalytic activity and therefore should be independent from the membrane. We suspect this improvement is due to higher catalyst utilization, which is made possible by a greater contact area of the catalyst layer and the directly deposited membrane. References: [1] M. Breitwieser, Direct membrane deposition as novel fabrication technique for high performance fuel cells, 2017, DOI: [2] S. Vierrath, M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele, The reasons for the high power density of fuel cells fabricated with directly deposited membranes, Journal of Power Sources, Volume 32

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