Iridium is a chemical element that belongs to the platinum group metals and is one of the rarest elements in the Earth's crust. This precious metal occurs naturally only in very low concentrations, which is why it is so rare. As a result, iridium is more valuable than gold and platinum. Global annual production amounts to only 7–9 metric tons. The main mining regions are in South Africa and Russia, where iridium is produced as a byproduct of platinum and nickel mining.
This silvery-white, high-gloss metal has the following properties:
- Extreme Hardness and Brittleness
- Exceptional corrosion resistance
- High temperature resistance (melting point: 2,466 °C)
- High density (22.56 g/cm³)
Significance for the hydrogen economy
In hydrogen technology, iridium plays a central role as a catalyst in PEM electrolyzers. This rare precious metal accelerates the oxygen evolution reaction (OER) at the anode. Its corrosion resistance and high catalytic activity enable efficient electrolysis processes at high current densities. Without iridium, water splitting would be significantly less efficient, the anodes would corrode quickly, and there would be greater energy losses due to overvoltage.
The combination of catalytic activity and corrosion resistance in acidic environments makes iridium indispensable for this application. Alternative materials generally exhibit either lower efficiency or dissolve during operation.
Challenges in Scaling
The scaling up of green hydrogen production is significantly limited by the limited availability of iridium. Calculations by various research institutes show:
- Given current electrolyzer designs and annual iridium production, it would only be possible to manufacture PEM electrolyzers with a total capacity of about 3–7 GW per year.
- However, the EU’s climate goals require an installed electrolyzer capacity of 40 GW in Europe alone by 2030. (Globally, the energy transition will require hundreds of gigawatts of electrolyzer capacity.)
The scarcity is also driving up prices: Iridium costs around 4,000–5,000 euros per troy ounce (31.1 grams). Reducing the demand for iridium would not only lower costs but also decrease dependence on this limited resource.
To overcome resource constraints, researchers are pursuing several strategies:
- Reduction of Iridium Loading Through Optimized Nanostructures and Carrier Materials
- Alloying with less expensive metals while maintaining the same performance
- Alternative catalytic converter systems based on other materials
- Innovative Coating Processes
Technologies that significantly reduce iridium consumption are considered a breakthrough for the hydrogen economy. A 90–95% reduction would increase the production capacity for electrolysers tenfold.
Recycling and the Circular Economy
Given the scarcity of iridium, its recycling is also becoming increasingly important. First-generation electrolyzers are gradually reaching the end of their useful life. The recovery of this precious metal from used catalytic converters is emerging as an important industry. Establishing a functioning circular economy for iridium is considered essential for the long-term hydrogen economy.
