ABSTRACT
Proton exchange membrane water electrolysis (PEMWE) is projected to become a key technology to enable the decarbonisation of ‘hard to abate’ sectors of the economy and was recently identified as a key pillar of JM’s future strategy. However, the technology’s reliance on iridium, one of the scarcest elements on Earth, as an oxygen evolution reaction catalyst, has led to uncertainty in both the scientific and policy-making communities over whether a large-scale PEMWE industry can be realised. This work investigates the future iridium demand of the global PEMWE sector and examines how different strategies can improve iridium utilisation in the anode catalyst, including the progress JM is making. Iridium utilisation targets necessary to avoid iridium supply limitations in the PEMWE sector, as set by policy-making bodies, are reviewed. Modelling the iridium demand of the PEMWE sector shows that iridium utilisation needs to improve by an order of magnitude by 2050 to avoid iridium supply limiting capacity expansion. Furthermore, closed-loop recycling of iridium would allow the installed capacity in 2050 to increase by ~170%. If these two conditions are met, global PEMWE capacity could reach 1.3 TW by 2050 using only 20% of annual global primary iridium supply, which PGMS consider to be realistic given future demand projections. Electrochemical data and modelling are used to identify the key levers JM is using to achieve the necessary reduction in iridium utilisation, as well as targets and strategies to enable us to go even further. Then, different types of iridium-based anode catalysts from the literature are compared against these targets using catalyst coated membrane (CCM) test data. This allows us to identify the need to place greater research focus on catalyst stability and the ability to make homogeneous catalyst layers at low iridium loadings. As a main result, it is found that a terrawatt-scale PEMWE industry can avoid being constrained by iridium supply as long as technological development of a similar level to that seen in PEM fuel cells and high iridium recycling rates are realised – two conditions fully aligned with JM’s core capabilities.
Slide deck: M Clapp PGM conference presentation July 2023
BIOGRAPHY
I joined Johnson Matthey after completing my studies in Natural Sciences (BA & MSc) at the University of Cambridge, specialising in physical and theoretical chemistry. For my first two years at JM I was on the science graduate programme, completing three different job roles in different parts of the company, spanning from science research to commercial planning and project management. I then joined the JM Technology Centre in Sonning Common, Reading, as a full-time scientist. My research focuses on understanding the electrochemistry of PGM catalysts used in water electrolysers and hydrogen fuel cells.