Performance of the RuO ₂ Catalyst Layer with Nonuniform Ionomer Distribution for Water Electrolysis

Proton exchange membrane water electrolysis (PEMWE) stands out as a promising technology for producing highly pure hydrogen at a high voltage efficiency and with minimal impact on the environment. The manufacturing method of the catalyst layer still needs more fine-tuning to improve the performance and lifetime of PEMWE even with notable progress in materials development. In this work, we showcase the sensitivity of the polarization at the RuO2 anode to the spatial distribution of the ionomer within the catalyst layer over short- and long-term operation. A series of anode electrodes with different formulations are systematically prepared and characterized to quantify the interplay between the components’ spatial distribution and the polarization behavior during water electrolysis. The results point to the more efficient utilization of the catalyst particles in a graded electrode, as substantiated by Tafel and voltammetry analysis. Electrochemical impedance spectroscopy identifies electronic and ionic charge transport as the dominant loss phenomena in the bulk and at interfaces, respectively. Our results suggest that the aging rate at the catalyst layer is influenced by the ionomer content and is higher close to the membrane. By exploring the formulation parameters of the graded catalyst layer, this work seeks to contribute to the development of more efficient PEM electrolysis systems, paving the way for a sustainable hydrogen economy.