There are extremely ambitious plans for rapid growth in hydrogen generation from renewables. PEM (polymer electrolyte membrane) electrolysis is particularly well suited to work with these intrinsically intermittent power sources due to their ability to duty cycle on the seconds timescale. An oft-sited liability of PEM is their reliance on precious group metal, PGM materials, specifically the use of Iridium for the oxygen evolution reaction (OER). Iridium is the rarest natural element on earth, with global production a scant 10 tons/year[1]. Speculation on increased demand has led to a recent price surge as well (Figure 1). Current Ir usage is estimated around 400 g Ir/MW of electrolysis[2]. This would put a cap of 25 GW/year of PEM electrolysis, assuming 100% of production was steered towards electrolysis, away from current uses, which include crucibles, chlor-alkali catalyst and spark plugs.

These perceived challenges have motivated a healthy increase in alkaline exchange membrane (AEM) electrolysis, which can operate without the use of PGMs. AEMs have yet to demonstrate suitable durability, and have other system implications. The iridium availability cap can be greatly increased, however, by lowering Ir loadings on an areal basis and increasing current density. Furthermore, platinum which is far more prevalent can be used as a substitute, however at the cost of efficiency. This talk will look at how much iridium is needed, the likelihood of increased production, the cost iridium in PEM electrolysis, the use of substitutes, either membrane or catalyst systems to determine if the total addressable market for hydrogen electrolysis can be met by PEM.

[1] M. Garside Statista, https://www.statista.com/statistics/585840/demand-for-iridium-worldwide/

[2] Ahmad Mayyas, Mark Ruth, Bryan Pivovar, Guido Bender, and Keith Wipke, Manufacturing Cost Analysis for Proton Exchange Membrane Water Electrolyzers. NREL, Aug, 2019. https://www.nrel.gov/docs/fy19osti/72740.pdf