Reduction of Iridium content in anode catalyst for PEM water electrolysis

This thesis, developed in collaboration with Toyota Motor Europe, presents the studies conducted on innovative materials to decrease the content of iridium in anode catalyst used for PEM water electrolysis. This study delves into an extensive literature review, aiming to identify new morphologies and chemistry that could meet the requirements. Although PEM water electrolysis is a promising technology for green hydrogen production, its reliance on scarce and costly iridium motivates the search for alternative catalysts with lower noble metal content. The objective of this work was to investigate the electrochemical performance of three different class of low-iridium catalysts, each characterized by distinct chemistry, morphology and synthesis methods. The experimental activity, carried out at Toyota Motor Europe laboratories, involved membrane electrode assembly (MEA) fabrication, single-cell testing, and electrochemical characterization through polarization curves and impedance analysis, interpreted using a Distribution of Relaxation Time (DRT) approach. This research demonstrated how both the composition and the synthesis route of the catalysts strongly influence the performance of the PEM electrolyzer. A deeper understanding of material behavior proved essential to optimize catalyst integration and reduce associated losses. Several limiting factors were identified across all samples, offering clear directions for further improvement. Among the tested materials, one catalyst with low content of Ir was selected as a particularly promising alternative to current benchmark solutions. Furthermore, this work laid the groundwork for applying the DRT approach to PEM electrolyzers, enabling the identification of distinct polarization processes and offering new insights into cell behavior under operating conditions. These findings provide a valuable foundation for the development of more sustainable and efficient PEMWE systems in future applications.