A Segmented Along the Channel Test Cell for Locally Resolved Analysis at High Current Densities in PEM Water Electrolysis

For the scale-up of proton exchange membrane (PEM) water electrolysis, understanding the cell behavior on industrial scale is a prerequisite. A proper distribution of current and temperature in the cell can improve performance and decrease overall degradation effects. Due to water consumption as well as the concomitant gas evolution and accumulation, gradients and inhomogeneities along the reaction coordinate are expected. These effects increase along the water supply channels of a flow field and are expected to lead to spatial gradients in cell performance and temperature. In this study we present a new test cell that is segmented along the flow field channels and is designed for the operation at high current densities. We show polarization curve measurements at 10 bar differential pressure up to 10 A∙cm-2 at 2.7 V without observing any mass transport limitations and conduct current density, temperature and impedance distribution measurements. At harsh conditions (low water flow rates of 2 ml∙min-1∙cm-2 and high current densities up to 6 A∙cm-2) we see significant temperature and current density increase of 13 K and 0.7 A∙cm-2 which can be explained by decreasing membrane resistance determined via EIS of >10 mΩ cm2 along the channel. The validity of the impedance measurements is proofed by comparison of the impedance at 100 mHz with the direct current resistance of the cell extracted by the local slope of the polarization curve.