Correlating Electrode Morphology with Electrochemical Properties in PEM Water Electrolysis MEAs after Variable Load Cycling

In operation of a proton exchange membrane (PEM) water electrolyzer, the applied electric field has direct impact on the overall cell performance. Thus, an electrochemical break-in procedure is often performed to activate the membrane electrode assembly (MEA) and optimize the cell performance, while accelerated stress tests allow an investigation of the cell durability and degradation behavior, including the MEA. However, the effect of an applied electric field on the electrochemical and correlated morphological properties of MEA electrodes has not been discussed so far. This work examines this influence on Ir black based anodes in commercial MEAs utilizing a multi-technique approach. Here, we present two in-house developed cells for operating an individual MEA electrode as the working electrode in a three-electrode configuration. The impact of MEA treatment in an oxidative environment under constant potential holds or dynamic potential profiles in 1 M H 2 SO 4 solution was examined in alternating current scanning electrochemical microscopy (AC-SECM) studies and by analyzing the double layer capacitance and electrochemical performance for the oxygen evolution reaction. The results show a clear correlation between the electrochemical response and morphological features from oxidation and agglomeration of catalyst material depending on the applied electric field. The exposure to the electric field reduced the anode surface impedance compared to the initial state. Furthermore, the amount of IrO x in the catalyst layer varied between the experimental protocols, directly impacting the density, porosity, electrical conductivity and electrochemical performance of agglomerated material.