OPINION | Will there be enough iridium available to meet the rising demand from PEM electrolysers?
There are several potential responses to the looming catalyst supply challenge, but none are guaranteed to solve the problem, writes Jacques Moss
The coming decades will see a dramatic increase in critical mineral demand associated with the adoption of low carbon technologies, from EVs to solar panels and battery storage. Rising demand will increase the risk of supply bottlenecks and elevated deployment costs.
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Within the hydrogen industry, material sourcing concerns are most acutely focused on iridium.
The metal is used to catalyse the oxygen evolution reaction within polymer electrolyte membrane (PEM) electrolyser cells, one of the two most commercially advanced technologies for producing green hydrogen.
PEM electrolysis represents a little under half of planned electrolyser manufacturing capacity, with leading players such as Plug Power, ITM Power and Cummins backing the technology due to its small footprint and suitability for use with intermittent renewable energy sources.
Although other material inputs for electrolysers (such as platinum, nickel, and copper) may also face supply constraints, iridium is of particular concern. The metal is found in extremely low concentrations in the earth’s crust — at approximately 0.000003 parts per million. It is only extracted as a by-product isolated during platinum and palladium production at an annual tonnage measured in the single digits.
No other material input will be so strongly influenced by future demand from the electrolyser industry. Moreover, no other material required is so geographically concentrated, with just one country — South Africa — responsible for close to 90% of global iridium output.
Meeting iridium demand from PEM electrolysis
There are several potential responses to meet rising demand for critical minerals.
A second option is improving rates of reuse and recycling. Within electrochemical applications, iridium recovery rates are already relatively high, at close to 50%. This still leaves significant scope for improvement, and rates above 90% may be attainable in the future.
Recovery levels across other applications, such as spark plugs or high-performance alloys, are unfortunately much lower due to the challenging economics of extracting materials at very low concentrations.
While circular economy solutions within the electrolyser industry will no doubt be critical over the long term, the long lifetimes of electrolyser installations and low levels of existing capacity mean that recycling will play only a very limited role in meeting demand during the initial scale-up period (through the mid-2030s).
A final option is reducing iridium catalyst loading within PEM electrolysers — in other words, improving the technology so that less iridium is required per kilowatt of electrolysis capacity deployed.
This approach is likely to yield the greatest benefits to manufacturers as the hydrogen economy scales up, and it is where the industry’s efforts will be focused.
Given the momentum behind PEM electrolysis, meeting iridium supply challenges will be essential to achieving hydrogen production targets worldwide.