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Advancements in green hydrogen production with rare metals
Boosting green hydrogen: Korean researchers reduce rare metals in production

By Daniel Lehewych
June 2, 2023

 

Green hydrogen, a key player in efforts towards a decarbonized economy, has been facing a major hurdle due to high production costs. As reported in Newswise, the costs primarily come from the need for expensive rare metals, such as iridium and platinum, used in polymer electrolyte membrane water electrolysis devices that produce this eco-friendly hydrogen. Yet, breakthrough technology from the Hydrogen and Fuel Cell Research Center at the Korea Institute of Science and Technology (KIST) could be a game-changer.

Green Hydrogen Breakthrough

Led by Dr. Hyun S. Park and Sung Jong Yoo, the research team has developed a way to significantly decrease the amount of platinum and iridium required in the protective layers of these electrolysis devices. Even better, this reduction doesn't compromise performance or durability – two crucial aspects of large-scale usage.

Here's the twist. Instead of focusing solely on reducing the quantity of iridium catalyst, as previous studies have done, these researchers have replaced the precious metal in the protective layer with inexpensive iron nitride, which possesses a large surface area. Then, a smaller quantity of iridium catalyst is uniformly coated over it. The result? A marked increase in the economic efficiency of the device.

Economic Efficiency Improved

These electrolysis devices play a crucial role in green hydrogen production, generating high-purity hydrogen and oxygen by decomposing water using renewable sources like solar power. In addition, they supply hydrogen to various industries, including steelmaking and chemicals. What's more, they are ideal for storing renewable energy as hydrogen energy, making the increased economic efficiency of these devices a vital stepping-stone in realizing a green hydrogen economy.

A key hurdle in the widespread adoption of these green hydrogen production devices has been the scarcity and low production of precious metals used in the machines. In standard electrolysis units, for instance, the oxygen-generating electrode that operates in a highly corrosive environment requires a protective layer of gold or platinum. On top of this, an iridium catalyst layer is coated. Unfortunately, both these metals have minimal reserves and production.

To enhance the economic feasibility of water electrolysis, the team at KIST replaced these rare metals with inexpensive iron nitride (Fe2N). A composite process was used to uniformly coat the electrode with iron oxide, which has low electrical conductivity, and then convert it to iron nitride to boost conductivity. On top of this iron nitride layer, an iridium catalyst about 25 nanometers thick was uniformly coated, reducing the quantity of iridium catalyst needed to less than 0.1 mg/cm2.

The developed electrode replaces gold or platinum used as a protective layer, maintaining performance comparable to existing commercial electrolysis units, and slashes the amount of iridium catalyst to just 10% of the current level. The team with these new components was operated for over 100 hours to verify its initial stability.

"Reducing the amount of iridium catalyst and developing alternative materials for the platinum protective layer is essential for the economic and widespread use of polymer electrolyte membrane green hydrogen production devices, and the use of inexpensive iron nitride instead of platinum is of great significance," said Dr. Hyun S. Park of KIST. "After further observing the performance and durability of the electrode, we will apply it to commercial devices soon."

 


 

 

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