Advanced Method for Voltage Breakdown Analysis of PEM Water Electrolysis Cells with Low Iridium Loadings

Abstract

Proton exchange membrane water electrolysis (PEMWE) is an established technology for hydrogen production. To meet the increasing demand and further reduce costs, there is a growing interest in reducing the iridium (Ir) loading. In recent works the complex interface between porous transport layer (PTL) and catalyst layer (CL) was identified as pivotal for PEMWE performance. In this study, this interface was systematically investigated for various Ir loadings and PTL types using a voltage breakdown analysis (VBA) method to differentiate between different sources for overpotential. As expected, the oxygen evolution reaction (OER) overpotential increases with decreasing Ir loading, but its extent depends on the CL/PTL interfacial contact area and the in-plane electrical conductivity of the CL. If the latter is low, this can be partly compensated by using a proper PTL counterpart. However, especially when using low Ir loadings, the VBA method results in inconclusive OER kinetic parameters such as the apparent exchange current density. Therefore, the constant Tafel slope voltage breakdown analysis (CT-VBA) method is proposed considering possible mass transport losses even at relatively small current densities within the Tafel fit regime. These findings provide insights to tackle challenges associated with reducing Ir loading.