Tracking Polarization and Passivation in Anion Exchange Membrane Electrolyzers via Current-Dependent Distribution of Relaxation Times of Electrochemical Impedance Spectroscopy

Abstract

Anion exchange membrane (AEM) electrolyzers are promising for sustainable hydrogen production, however, still suffer from limited lifetime, high degradation rates, and remain a complex system to monitor. In this work, galvanostatic EIS combined with DRT analysis enabled the deconvolution of OER, HER, and ion transfer contributions. The break-in effect was observed and quantified, with decreasing polarization resistances in early operation. The activation of the NiFe hydroxide catalyst into NiOOH was tracked, showing improved OER kinetics within 24 h. Low-frequency features were attributed to corrosion of the nickel porous transport layer (PTL) and formation of a passivation layer, confirmed by XPS. While overall performance remained stable after 48 hours at 1 A cm-2, an increase in ohmic resistance was observed due to interfacial effects.