Inspenet, December 24, 2023.
Green hydrogen from salt water
A new initiative led by Professor Mingxin Huang, from the Department of Mechanical Engineering of the University of Hong Kong (HKU), has developed an innovative type of steel with significant corrosion resistance, intended for the production of green hydrogen through the use of salt water, easily accessible in our oceans.
Although the cost of this new steel is considerably lower compared to its current equivalents, its performance in a salt water electrolyzer is comparable to conventional industrial practice that employs titanium as a key structural component for the generation of green hydrogen from desalinated or acidic seawater. The invention involves the addition of a manganese secondary layer designed over the chromium prelayer at ~720 mV onto the single Cr2O3-based passive layer.
Since there is a general consensus that manganese decreases the ability of stainless steel to resist corrosion , scientists were initially skeptical of the new role attributed to this material. This skepticism arises because the finding of Mn-based passivation is counterintuitive and challenges conventional understanding of corrosion science.
“However, when numerous results were presented at the atomic level, we were convinced. Beyond our surprise, we are eager to exploit the mechanism” says Dr Kaiping Yu, first author of the paper, whose PhD is supervised by Professor Huang.
Currently, the total cost of a 10 MW PEM electrolysis system is estimated to be $2.8 million and up to 53% of this cost is attributed to structural components. Thanks to the innovation of the group led by Huang, it is now possible to use steel instead of conventional structural elements, such as gold and platinum, which are considerably more expensive.
According to estimates, the implementation of stainless steel for hydrogen could reduce the cost of structural materials by approximately 40 times.
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