Evaluating the Effects of Clamping Force Variations on Performance and Current Distribution in PEM Electrolysis Cells

This study presents an experimental investigation into the influence of varying clamping forces on the electrochemical performance and current density distribution in PEM water electrolysis cells. High-resolution segmented current measurement boards from DILICO engineering GmbH were employed in combination with a precisely adjustable single-cell setup provided by BalticFuelCells GmbH. The relationship between mechanical compression, contact resistance, and local current distribution was analyzed in detail through segmented in-situ current density measurements. The results demonstrate that a moderate increase in clamping force (1.2–1.4 MPa) leads to a significant improvement in cell performance. This is reflected in more homogeneous current distributions and reduced ohmic losses. For instance, at 1.2 MPa, a reduction in the standard deviation of current density by approximately 25% was observed. At the same time, polarization (UI) curves within this pressure range showed lower cell voltages for identical current densities. However, above 1.6 MPa, performance declined again, caused by excessive compression, mechanical deformation of the porous transport layers (PTLs) and localized membrane dehydration. The study identifies an optimal clamping force range that balances mechanical stability and electrochemical efficiency. The findings provide valuable design guidelines for the development of durable and efficient PEM electrolysis systems and emphasize the importance of mechanically optimized operating parameters.