Groundbreaking stainless “Super Steel” generates sustainable hydrogen production from seawater
Stainless steel for hydrogen paved the way for cost-effective and corrosion-resistant structural components in water electrolysis systems
[Nov. 22, 2023: JJ Shavit, The Brighter Side of News]
The novel stainless steel for hydrogen developed by the team. (CREDIT: Hong Kong University (HKU))
In a groundbreaking research project led by Professor Mingxin Huang at the Department of Mechanical Engineering of the University of Hong Kong (HKU), a remarkable advancement in stainless steel technology has emerged, potentially revolutionizing the field of green hydrogen production.
The development, known as stainless steel for hydrogen (SS-H2), has paved the way for cost-effective and corrosion-resistant structural components in water electrolysis systems, offering a promising solution for sustainable hydrogen production.
This achievement marks the latest triumph in Professor Huang's illustrious career, following the development of anti-COVID-19 stainless steel in 2021 and the creation of ultra-strong and ultra-tough Super Steel in 2017 and 2020, respectively.
Professor Mingxin Huang and Dr Kaiping Yu. (CREDIT: HKU)
The Significance of SS-H2
The SS-H2, the result of six years of dedicated research, possesses exceptional corrosion resistance, particularly in saltwater environments. This breakthrough opens up the possibility of utilizing SS-H2 in green hydrogen production processes from seawater—a novel sustainable approach still in the developmental stages. The steel's performance in saltwater electrolysis matches that of the current industrial practice employing titanium as structural parts, yet it comes at a significantly lower cost.
Professor Huang's team achieved this feat through what they term a "sequential dual-passivation" strategy. Contrary to conventional wisdom, this innovative approach combines two passivation layers, one based on chromium (Cr) and the other on manganese (Mn), resulting in a stainless steel alloy with unparalleled corrosion resistance. The Mn-based layer forms on top of the Cr-based layer, effectively preventing corrosion in chloride media up to an ultra-high potential of 1700 mV. This represents a fundamental breakthrough in stainless steel technology, addressing a long-standing limitation in conventional stainless steel.
"Initially, we did not believe it because the prevailing view is that Mn impairs the corrosion resistance of stainless steel. Mn-based passivation is a counter-intuitive discovery, which cannot be explained by current knowledge in corrosion science. However, when numerous atomic-level results were presented, we were convinced. Beyond being surprised, we cannot wait to exploit the mechanism," said Dr. Kaiping Yu, the first author of the paper.
Industrial Application and Cost Reduction
One of the most significant implications of this discovery is the potential cost reduction in green hydrogen production systems. Currently, water electrolyzers in desalted seawater or acid solutions require expensive gold (Au)- or platinum (Pt)-coated titanium (Ti) for structural components.
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For example, the structural components contribute up to 53% of the total cost of a 10-megawatt PEM electrolysis tank system, which amounts to approximately HK$17.8 million. However, Professor Huang's SS-H2 offers a cost-effective alternative, estimated to reduce the expense of structural materials by approximately 40 times, making it highly attractive for industrial applications.
"From experimental materials to real products, such as meshes and foams, for water electrolyzers, there are still challenging tasks at hand. Currently, we have made a big step toward industrialization. Tons of SS-H2-based wire has been produced in collaboration with a factory from the Mainland. We are moving forward in applying the more economical SS-H2 in hydrogen production from renewable sources," added Professor Huang.
Stainless steel has been a crucial material in corrosive environments for over a century, with its corrosion resistance primarily dependent on the presence of chromium. A passive film forms on stainless steel through the oxidation of chromium (Cr), protecting it from corrosion in natural environments. However, the conventional single-passivation mechanism relying on Cr has limited further advancements in stainless steel. The stable Cr2O3 passive layer can be further oxidized into soluble Cr(VI) species, leading to transpassive corrosion, typically occurring at potentials below that required for water oxidation.
The present “sequential dual-passivation” strategy enlarges the passive region of stainless steel to high potentials above water oxidation, enabling them as potential anodic materials for green hydrogen production via water electrolysis. (CREDIT: Science Direct)
Even 254SMO super stainless steel, renowned for its superior pitting resistance in seawater, is susceptible to transpassive corrosion at higher potentials. Professor Huang's team tackled this challenge by developing the SS-H2 using a "sequential dual-passivation" approach, which surpassed the limitations of conventional stainless steel. The additional Mn-based passivation layer formed on top of the Cr-based layer at approximately 720 mV successfully prevented corrosion in chloride-rich environments up to an impressive potential of 1700 mV.
How can green hydrogen be used by industry?
Green hydrogen can be used in industry in a variety of ways, including:
Ammonia production: Hydrogen is a key component in the production of ammonia, which is used in a wide range of industrial applications, including fertilizers, plastics, and explosives. Green hydrogen can be used to produce ammonia without emitting greenhouse gases.
Oil refining: Hydrogen is used in oil refining to remove sulfur from crude oil. This process, known as hydrotreating, produces cleaner-burning fuels and reduces emissions. Green hydrogen can be used to hydrotreat crude oil without emitting greenhouse gases.
Methanol production: Hydrogen is also used in the production of methanol, which is a versatile fuel that can be used in transportation, power generation, and other applications. Green hydrogen can be used to produce methanol without emitting greenhouse gases.
Steelmaking: Hydrogen can be used to reduce iron ore in the production of steel. This process, known as direct reduction, produces less emissions than traditional methods of steelmaking. Green hydrogen can be used to reduce iron ore without emitting greenhouse gases.
Other industrial applications: Green hydrogen can also be used in other industrial applications, such as glassmaking, electronics manufacturing, and food processing.
The use of green hydrogen in industry has the potential to significantly reduce greenhouse gas emissions and help to decarbonize the global economy. However, the cost of green hydrogen is still relatively high, so there is a need to scale up production and reduce costs in order to make it more competitive with fossil fuels.
Companies that are using green hydrogen in industry:
Shell: Shell is one of the world's leading oil and gas companies, and it is also a major player in the green hydrogen market. Shell is developing green hydrogen projects in a number of countries, including Australia, Germany, and the Netherlands.
Linde: Linde is a leading industrial gases company, and it is also a major player in the green hydrogen market. Linde is developing green hydrogen projects in a number of countries, including the United States, China, and Japan.
Bloom Energy: Bloom Energy is a company that develops and manufactures fuel cells that produce electricity from hydrogen. Bloom Energy's fuel cells are used in a variety of applications, including data centers, hospitals, and manufacturing facilities.
The Future of SS-H2
Professor Huang and his team's innovative approach to stainless steel development has the potential to reshape industries reliant on corrosion-resistant materials. As the SS-H2 technology progresses toward industrialization, its affordability and remarkable corrosion resistance may unlock new possibilities in green hydrogen production and other applications. This breakthrough serves as a testament to the power of scientific innovation and its capacity to drive positive change in our quest for sustainable and eco-friendly solutions.
For more green news stories check out our Green Impact section at The Brighter Side of News.
Note: Materials provided above by Tel-Aviv University. Content may be edited for style and length.
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