Investigation of the degradation of proton exchange membrane water electrolysis cells using electrochemical impedance spectroscopy with distribution of relaxation times analysis

Reduction of catalyst loading on Proton Exchange Membrane (PEM) Electrolysis Cells (EC) is needed because of scarcity and high price of the catalyst. Monitoring the degradation of these cells is important to be able to allocate the different processes taking place. Electrochemical Impedance Spectroscopy (EIS) might be suitable for this purpose, but in its usual implementation, the system and the contribution of its components to the total resistance must be already known to build a suitable equivalent circuit model (ECM). Furthermore, the overlap of different processes in the Nyquist and Bode plots hinders the identification of single components of the system. The Distribution of Relaxation Times (DRT) analysis converts the EIS data into a distribution of time constants of individual processes. The contribution of each component to the full cell resistance can be identified by varying different operation parameters. In this work, a PEMEC with low iridium loading was analyzed by DRT and the faradaic processes were identified. A long-term test was carried out and the degradation of the cell was investigated by DRT analysis, to determine the components and processes which limit the cell performance.