Low-Iridium Catalysts at Commercial Scale

Iridium usage in PEMWE anodes presents a potential bottleneck in the scale-up of this promising technology. While the DOE focusses on reducing total PGM loading 1 , the primary restriction lies in the supply of Iridium specifically. Mining operations only output ~7 tonnes of Iridium per year (as a by-product of platinum mining) 2 , which would cap PEMWE installations at 2 GW per year 2 , at current Iridium loading. The prevalence of supported Iridium materials in the literature indicates an inclination to follow the same path as PEMFC catalysts- wherein the supporting of Pt nanoparticles on carbon structures provides both a clear performance improvement, and a means of simplifying and easing the synthetic process. Supporting of Iridium catalysts poses a much more complex picture, with the process often providing no significant increase in intrinsic activity and complicating the synthetic process- a key consideration when addressing an issue (Iridium supply bottleneck) which only affects GW-scale manufacturing. A low-Iridium catalyst which is limited to gram-scale production is of no use. We present an alternative path to low-Iridium PEMWE technology. Utilising a solid solution of IrRuOx, we demonstrate a catalyst family capable of meeting or exceeding the 2026 DOE technical targets 1 at low Iridium loadings. We demonstrate the stability of the ruthenium component (a concern we see frequently in the market), and most importantly, demonstrate a route to GW-scale low-Iridium PEMWE technology which can be deployed today. 1 https://www.energy.gov/eere/fuelcells/technical-targets-proton-exchange-membrane-electrolysis 2 https://doi.org/10.1016/j.ijhydene.2021.04.174. “Is iridium demand a potential bottleneck in the realization of large-scale PEM water electrolysis?”, Minke et al., 2021.