Abstract 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. At high current densities (> 5 A∙cm-2) these effects are anticipated to be critical due to the high amount of gas produced and the increased degradation rate resulting from the high overpotentials. 
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 of up to 10 A∙cm-2. With this approach it is possible to analyze performance gradients and the spatial distribution of loss processes under industry-relevant conditions by measuring the current density and temperature distribution and by performing locally resolved electrochemical impedance spectroscopy (EIS).
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