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The material, which was developed by researchers at the Korea Institute of Science and Technology (KIST), could help reduce the price of green hydrogen.
The fuel can be made using water electrolysis, which uses renewable energy to split water into hydrogen and oxygen. The production cost of green hydrogen is about $5 per kilogram however – two- to three-times higher than grey hydrogen, which is obtained from natural gas.
Water electrolysis must therefore be improved to make green hydrogen use practical, the researchers said. This could be particularly important in Korea, where use of renewable energy is limited by geographical constraints.
Dr Kyung-Joong Yoon’s research team at KIST’s Energy Materials Research Centre developed the new nanocatalyst for high-temperature water electrolysis. The material can retain a current density of more than 1A/cm2 for a long time, at temperatures above 600ºC.
To improve the performance and stability of water electrolysis cells, the team investigated the degradation mechanisms of nanomaterials at high temperatures and identified reasons for abnormal behaviour.
Electrolysis technology can be classified into low- and high-temperature electrolysis. While low-temperature electrolysis at below 100ºC has been developed for a long time and is technologically more mature, high-temperature electrolysis above 600ºC offers higher efficiency. Commercialisation has been hindered by the lack of thermal stability and insufficient lifetime owing to high-temperature degradation, such as corrosion and structural deformation.
Nanocatalysts, which are used to improve the performance of low-temperature water electrolysers, quickly deteriorate at high operating temperatures, making it difficult to effectively use them for high-temperature water electrolysis.
To overcome this limitation, the team developed a new technique for nanocatalyst synthesis, which suppresses the formation of compounds that can cause degradation.
By systematically analysing nanoscale phenomena using transmission electron microscopy, the researchers identified specific substances causing severe structural alterations, such as strontium carbonate and cobalt oxide. They successfully removed those materials to achieve highly stable nanocatalysts, in both chemical and physical properties.
When the team applied the nanocatalyst to a high-temperature water electrolysis cell, it more than doubled the hydrogen production rate and operated for more than 400 hours at 650ºC without degradation. The technique was also applied to a large-area water electrolysis cell, which the team said confirms its “strong potential for scale-up and commercial use”.
“Our newly developed nanomaterials achieved both high performance and stability for high-temperature water electrolysis technology, and it can contribute to lower the production cost of green hydrogen, making it economically competitive with grey hydrogen in the future,” said Dr Yoon. “For commercialisation, we plan to develop automated processing techniques for mass production, in cooperation with industry cell manufacturers.”
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