2023-05-02 15:00:24
Dhe recipe seems very simple. To produce hydrogen, an electrolyser only needs electricity, if possible green, of course, and water. And in a fuel cell, the whole thing runs backwards, of course it needs the oxygen previously extracted from the water. In order for these processes to work efficiently at low temperatures, however, another ingredient is required, the catalyst material.
It does not take part in the reaction itself, so theoretically it is not consumed. However, the precious metals used in the catalyst, especially platinum in fuel cells and iridium in electrolysers, determine the price of the systems to a large extent. The catalyst accounts for around 40 percent of the total costs of a fuel cell system.
Toyota wants to have significantly reduced the precious metal content in the drive of the new Mirai generation, but does not give any exact values. With iridium, it’s not just the cost that’s a problem, but also the availability. The transition metal is extremely rare. The German Raw Materials Agency estimates global production at seven tons and demand five times that in 2040.
“Like a kitchen sponge”
Theoretically, it would be very easy to significantly reduce the precious metal content if only as much material was used as is required for perfect function. In reality, however, the effectiveness of the catalytic converter steadily decreases over its useful life. The causes include contamination and clumping of the material caused by heat input. The latter cause the surface area effective during catalysis to decrease.
After ten years of development work, Pajarito Powder, a small company in which Hyundai Motors has a stake, claims to have found a solution. The company, based in New Mexico, USA, uses a very fine-pored carbon matrix as the carrier material for fuel cell catalytic converters. It encloses the platinum grains “like a kitchen sponge,” explains Thomas Stephenson, one of the founders. This protects the precious metal from contamination and prevents it from clumping, while the exchange of fluids is nevertheless unhindered. It should be possible to halve the platinum content without jeopardizing the durability of the fuel cell system. A similar technology is said to be able to reduce the iridium content in electrolysers by at least 40 percent.
The catalyst material is delivered as a powder that can be applied to the membrane-electrode assembly of a fuel cell using a printing-like process. Production of small quantities is scheduled to start this year.
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