The effect of compression on PEM Electrolyzer membrane electrode Assemblies

Reliable operation of polymer electrolyte membrane electrolysers requires a sound understanding of the effects surrounding the cell assembly. This work focues on the compression of the membrane electrode assembly (MEA) during cell assembly, which strongly influences cell performance, safety and lifetime of the electrolyser. In this work, we analysed the effect of increasing MEA compression on membrane deformation under the flow-fields land and channel regions and correlated structural changes to changes in cell performance. Via an overpotential break-down analysis, the main losses caused by membrane deformation due to cell compression were elucidated, supported by a structural analysis of cryogenic cross-sections of the used catalyst coated membranes (CCMs). Based on these results, an optimal cell compression between 30 and 40 % for the cell design used in this work to balance opposite trends of ohmic vs. mass transport overpotentials. In addition it was shown that the compressed membrane does not flow into the channel areas of the flow field, but rather into the pores of the porous transport layer.