Develop technologies to reduce the cost of producing green hydrogen

(Nanowerk News) Green hydrogen, which generates hydrogen without the use of fossil fuels or carbon dioxide emissions, has become increasingly important in recent years as part of efforts to achieve a zero-carbon economy. However, due to the high cost of producing green hydrogen-generating water electrolysis devices, the economic feasibility of green hydrogen is not very high.

Technological developments that drastically reduced the amount of rare metals such as iridium and platinum used in polymer electrolyte membrane water electrolysis devices paved the way for lowering production costs.

A research team led by Dr. Hyun S. Park and Sung Jong Yoo of the Hydrogen and Fuel Cell Research Center at the Korea Institute of Science and Technology (KIST) announced that they have developed a technology that can significantly reduce the amount of platinum and iridium, precious metals used in protective coatings on device electrodes. polymer electrolyte membrane water electrolysis, and safe performance and durability equivalent to existing devices (Application of Environmental B Catalysis, “High performance water electrolyzer with minimum use of platinum group metals: Iron nitride–iridium oxide core–shell nanostructures for stable and efficient oxygen evolution reactions”). The form of the catalyst is made by new technology (red-iridium/green-iron nitride catalyst). (Image: Korea Institute of Science and Technology)

Specifically, unlike previous studies that focused on reducing the amount of iridium catalyst while maintaining structures that use large amounts of platinum and gold as electrode shielding coatings, the researchers replaced the precious metal in the electrode shielding coating with inexpensive iron nitride. large surface area and evenly coating a small amount of iridium catalyst on it, greatly increasing the economic efficiency of the electrolysis device.

The polymer electrolyte membrane water electrolysis device is a device that generates high purity hydrogen and oxygen by decomposing water using electricity supplied by renewable energy such as solar power, and plays a role in supplying hydrogen to various industries such as steelmaking and chemicals. In addition, converting energy to store renewable energy as hydrogen energy is advantageous, so increasing the economic efficiency of these devices is critical to realizing a green hydrogen economy.

In a typical electrolytic device, there are two electrodes producing hydrogen and oxygen, and for the oxygen generating electrode, which operates in a highly corrosive environment, gold or platinum is plated on the surface of the electrode at 1 mg/cm22 as a protective layer to ensure durability and production efficiency, and 1-2 mg/cm22 an iridium catalyst is coated on top of it. The precious metals used in these electrolysis devices have very low reserves and production, which are the main factors hindering the widespread adoption of green hydrogen production devices. Schematic of the electrode fabrication process for this development. (Image: Korea Institute of Science and Technology)

To improve the economics of water electrolysis, the team replaced the rare metals gold and platinum used as protective coatings for oxygen electrodes in a polymer electrolyte membrane hydrogen production device with iron nitride (Fe).2N). To do so, the team developed a composite process that first coats the electrode with iron oxide, which has a low electrical conductivity, and then converts the iron oxide to iron nitride to increase its conductivity.

The team also developed a process that uniformly coats a 25 nanometer (nm) thick iridium catalyst over a protective layer of iron nitride, reducing the amount of iridium catalyst to less than 0.1 mg/cm.2produce electrodes with high hydrogen production efficiency and resistance.

The developed electrode replaces the gold or platinum used as a protective layer for oxygen generating electrodes with non-noble metal nitrides while maintaining performance similar to existing commercial electrolysis units, and reducing the amount of iridium catalyst to 10% of existing levels. Additionally, the electrolysis unit with new components was operated for over 100 hours to verify its initial stability.

“Reducing the amount of iridium catalyst and developing alternative materials for platinum protective coatings is essential for the economical use and widespread use of polymer electrolyte membrane green hydrogen production devices, and the use of inexpensive iron nitride instead of platinum is essential,” said Dr Hyun S. Park of KIST. . “After further observing the performance and durability of the electrodes, we will apply it to commercial devices in the near future.”