Green Hydrogen via PEM Electrolysis – Avoiding Iridium Supply Limitations

Abstract

The reliance of proton exchange membrane water electrolysis (PEMWE) on iridium as an oxygen evolution catalyst has led to uncertainty over whether a large-scale PEMWE industry can be realised. The future PEMWE capacity growth that is sustainable in terms of iridium supply is investigated. It is found that, if optimistic improvements in iridium utilisation and high recycling rates are achieved, a global capacity of 1.3 TW could be reached by 2050, which is above the Net-Zero Emissions 2050 target, using only 20% of annual primary iridium supply. The different catalyst strategies that can improve iridium utilisation are compared using membrane electrode assembly (MEA) testing data from the literature, with the order found to be supported nanoparticles ≈ extended surface structures > mixed oxides > nanoparticles. As a main result, it is found that a terrawatt-scale PEMWE industry can avoid being constrained by iridium supply if technological development of a similar level to that seen in PEM fuel cells is realised.