Mechanical Stability of Membranes in PEMWE
Authors: Kink Julian , Ise Martin , Suermann Michel , Bensmann Boris , Junker Philipp , Hanke-Rauschenbach Richard 
Published: December 2024

This study investigates the structural mechanics of membranes in proton exchange membrane water electrolysis (PEMWE) cells, with a particular focus on mechanical stressors and the resultant membrane deformation. Membrane defects such as cracks, pinholes, and thinning can occur due to mechanical stressors. Structural mechanical simulations can predict the membrane behaviour under stress if the boundary conditions are set accurately and the material models are chosen to fit experimental data. This presentation describes such model-based investigations and is divided into three parts. It begins with a general investigation of mechanical membrane behaviour in a PEMWE cell, followed by investigations regarding two different membrane reinforcing methods.

Firstly, the study examines the mechanical stress exposure of Nafion® 117 membranes within PEMWE cells, with a focus on the gap geometry between the cell frame and porous transport layers (PTL). Using a finite-element analysis, mechanical stresses and strains on the membrane during assembly and PEMWE cell operation are quantified. For this purpose, a suitable material model was implemented and parameterized based on experimental data. The results of the cell simulation demonstrate that no critical states arise with a gap size of 0.15 mm, even under differential pressure up to 10 bar. However, increasing the gap sizes to over 0.3 mm can lead to membrane buckling, resulting in membrane thinning, possibly followed by membrane failure. [1]

Secondly, the potential of reinforcing the membrane with a subgasket layer outside the active area is explored. Subgaskets can be used as a reinforcing layer for the membrane and are usually glued to the membrane. This study shows that subgasket layers can stabilize the membrane at the gap interface, even under differential pressure. However, this study highlights the need for careful positioning and thickness considerations of the subgasket for optimal mechanical stabilization. Furthermore, it was found that a subgasket can prevent membrane buckling, which can occur at increased gap sizes between cell frame and PTL. [2]

Lastly, the use of woven web layers within the membrane structure is assessed as a reinforcement strategy to avoid membrane defects. Our findings suggest that no failure is expected during normal operation with applied woven web reinforcement, including varied temperatures and differential pressure, unless the gap size at the edge of the electrochemically active cell area exceeds 0.1 mm. [3]

In conclusion, the research indicates that the choice of gap size in cell designs is crucial for preventing mechanical failures in PEMWE membranes. Additionally, the application of a reinforcement, such as a subgasket layer or woven web, can significantly enhance membrane stability, particularly at the gap interface. However, the thickness and the positioning of the subgasket must be carefully considered for optimal results.

J. Kink, M. Ise, B. Bensmann and R. Hanke-Rauschenbach, J. Electrochem. Soc.(170), 54507 (2023).

J. Kink, M. Suermann, M. Ise, Boris Bensmann, P. Junker and R. Hanke-Rauschenbach, Int. J. Hydrogen Energy (2024 (submitted)).

J. Kink, M. Ise, B. Bensmann, P. Junker and R. Hanke-Rauschenbach, J. Electrochem. Soc.(170), 114513 (2023).

Figure 1