Toshiba technology to cut iridium usage in electrolysis

PEM uses iridium, one of the rarest of all traded precious metals, as the catalyst in its electrodes.

Toshiba Corporation has developed a large-scale production technology for the electrodes that realize high-level efficiency in Power to Gas (P2G) technology, essential know-how for advancing toward a carbon-neutral society while reducing the use of iridium to 1/10.

P2G uses water electrolysis to convert renewable energy into hydrogen for storage and transportation to where it is needed. Polymer Electrolyte Membrane (PEM) electrolysis is seen as a highly promising conversion method, as it reacts rapidly to power fluctuations and is highly durable.

Toshiba developed an iridium oxide nanosheet laminated catalyst that reduced the iridium requirement to 1/10 in 2017. The company has now developed large-scale production technology that deposits the catalyst over a maximum area of 5m2 at one time. This advance is expected to drive forward the early commercialization of P2G for large-scale power conversion and contribute to the realization of carbon neutrality. Toshiba is aiming for commercialization in FY2023 or after.

PEM uses a membrane electrode assembly (MEA) that integrates the electrolyte membrane and electrode. Large-scale hydrogen conversion of electricity requires a large number of MEAs.

However, the MEA electrode relies on a large amount of iridium to ensure sufficient electrolytic efficiency. Iridium is one of the rarest precious metals. The practical application requires reducing the iridium used, a real challenge.

Forming electrodes requires a uniform coating of fine iridium oxide particles, but reducing the iridium oxide results in uneven application and non-uniform reactions that degrade water electrolysis performance.

Using Toshiba’s laminated nanosheet structure in the catalyst layer successfully reduces the required iridium to 1/10, while maintaining the water electrolysis performance. It also significantly expands the deposition surface area. As sputtering is conducted in a vacuum, deposition on a large area is difficult.

However, by modifying the deposition distribution ratio for multiple metal targets, including iridium, and the oxygen input level, Toshiba has successfully developed a large-scale production technology that realizes catalyst deposition on an area of up to 5m2 at a time.

In collaboration with Toshiba Energy Systems & Solutions Corporation, Toshiba has built MEA prototypes with electrodes based on the developed technology and has begun evaluation testing with a water electrolyzer manufacturer. Going forward, the company will improve the yield and quality toward mass production of MEA, aiming for commercialization in 2023 or after.

Zohaib Ali

Zohaib is the editor of H2 Bulletin. Please click on the email icon to contact me if you want to talk about a news.
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