What's the Status Quo of Performance and Durability for Low-Iridium Loadings with Commercial Catalysts in PEM Water Electrolysis?

Iridium scarcity and the associated challenges for the large-scale deployment of PEM water electrolyzer technology have been addressed in several studies. To meet the targets, several studies have shown that the iridium specific power density needs to be optimized to < 0.10 mg Ir W -1 . 1,2 However, the current state of the art is fuzzy and it's unclear how far we need to go to achieve large-scale deployment of the PEM water electrolyzer. Therefore, we have analyzed four different commercially available catalysts to determine where the current limitations are in realizing large-scale deployment of PEM water electrolysis. Using a common N115 Nafion membrane, we compared the performance for loadings ranging from 0.1 mg Ir cm -2 to 0.8 mg Ir cm -2 using one catalyst from Alfa Aesar and Umicore together with two catalysts from Heraeus. Sheet resistance was investigated for all loadings and catalysts and correlated with corresponding high frequency resistance and performance. Durability was evaluated using a bottom-up approach, starting with the lowest loading and a total test time of 500 h. With the data presented, we shed light on the current state of the art for low iridium loading in PEM water electrolysis. Literature Minke, C., Suermann, M., Bensmann, B. & Hanke-Rauschenbach, R. Is iridium demand a potential bottleneck in the realization of large-scale PEM water electrolysis? Int. J. Hydrog. Energy 46 , 23581–23590 (2021). Clapp, M., Zalitis, C. M. & Ryan, M. Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis. Catal. Today 420 , 114140 (2023).