Stainless steel can be used in a number of hydrogen production
techniques, especially those that involve steam methane reforming and
electrolysis.
In terms of steam methane reforming, the material is used in the
construction of reformers, heat exchangers, and other components of the process
as it is particularly well-suited to withstand high temperatures and corrosive
environments.
In terms of water electrolysis, the material is often used in
the construction of electrolyzers due to its corrosion resistance and
durability in the process’ harsh electrolytic environment.
Green hydrogen from
our oceans
Now, a new initiative spearheaded by Professor Mingxin Huang
at the Department of Mechanical Engineering of the University of Hong Kong
(HKU) has created a novel kind of steel with strong resistance to corrosion
that may be used in the manufacture of green hydrogen from saltwater easily
acquired from our oceans.
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The invention consists of adding a secondary manganese
(Mn)-based layer engineered on the preceding chromium (Cr)-based layer at ~720
mV onto the single Cr2O3-based passive layer. Because the general consensus is
that Mn reduces stainless steel's ability to withstand corrosion, the
scientists did not first accept the material’s new role. This is because the
discovery of Mn-based passivation is counterintuitive and defies conventional
corrosion science understanding.
Reducing the cost of
production by 40 times
At present, the total cost of a 10-megawatt PEM electrolysis
tank system is estimated to be HK$17.8 million (USD $ 2.8 million), of which up
to 53 percent is attributed to the structural components. Thanks to the
innovation of Huang's group, steel may now be used in place of traditional
pricey structural elements such as gold (Au) and platinum (Pt). According to
estimates, stainless steel for hydrogen (SS-H2) will reduce structural material
costs by approximately 40 times.
“From experimental materials to real products, such as meshes
and foams, for water electrolysers, there are still challenging tasks at hand.
Currently, we have made a big step toward industrialisation. 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,” explained Huang.
The researcher’s team is also behind the development of
anti-COVID-19 stainless steel first introduced in 2021, and ultra-strong and ultra-tough
Super Steel engineered in 2017 and 2020 respectively.
Study
abstract:
Stainless steel is critical material used in a wide variety of
industries. Unfortunately, current development of stainless steel has reached a
stagnant stage due to the fundamental limitation of the conventional Cr-based
single-passivation mechanism. Here, we show that, by using a sequential
dual-passivation mechanism, substantially enhanced anti-corrosion properties
can be achieved in Mn-contained stainless steel, with a high breakdown
potential of ∼1700
mV (saturated calomel electrode, SCE) in a 3.5 wt% NaCl solution. Specifically,
the conventional Cr-based and counter-intuitive Mn-based passivation is
sequentially activated during potentiodynamic polarization. The Cr-based
passive layer prevents corrosion at low potentials below ∼720 mV(SCE), while the Mn-based passive
layer resists corrosion at high potentials up to ∼1700 mV(SCE). 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.