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December 14, 2022
By Deena
Theresa
Engineers use sound waves to boost
green hydrogen production by 14 times
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Researchers at the RMIT University in Australia have figured out an
innovative, promising way to increase the production
of green hydrogen by 14 times - by employing sound waves through
electrolysis to split water.
According to the engineers, their invention could significantly reduce
green hydrogen production costs.
"One of the main challenges of electrolysis is the high cost of
electrode materials used, such as platinum or iridium," RMIT associate
professor Amgad Rezk, who led the work, said
in a statement.
"With sound waves making it much easier to extract hydrogen from
water, it eliminates the need to use corrosive electrolytes and
expensive electrodes such as platinum or iridium. As water is not a
corrosive electrolyte, we can use much cheaper electrode materials
such as silver," Rezk explained.
The research is published in Advanced
Energy Material, and an
Australian provisional patent application has been filed to protect
the new technology, as per the release.
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RMIT University
PhD researcher Yemima Ehrnst holding the acoustic device the research
team used to boost the hydrogen production, through electrolysis to split
water.
How is electrolysis used to produce
green hydrogen?
Electricity is run through water employing two electrodes to split
water molecules into oxygen and hydrogen gases. This process produces
green hydrogen, which signifies only a "small fraction" of global
hydrogen production due to the high energy required.
So, how is most hydrogen produced? By splitting
natural gas, also known as blue hydrogen. Natural gas emits
greenhouse gases into the atmosphere.
In their experiment, the RMIT engineers used high-frequency vibrations
to "divide and conquer" individual water molecules during
electrolysis.
"The electrical output of the electrolysis with sound waves was about
14 times greater than electrolysis without them, for a given input
voltage. This was equivalent to the amount of hydrogen produced,"
first author Yemima Ehrnst said.
The breakthrough is a huge step toward
using the "new acoustic platform"
Ehrnst added that the sound
waves also "prevented the build-up of hydrogen and oxygen bubbles
on the electrodes, which greatly improved its conductivity and
stability".
"Electrode materials used in electrolysis suffer from hydrogen and
oxygen gas build-up, forming a gas layer that minimizes the
electrodes’ activity and significantly reduces its performance," said
Ehrnst, a Ph.D. researcher at RMIT’s School of Engineering.
Professor Leslie Yeo, one of the lead senior researchers, said that
the breakthrough was a huge step toward using the "new acoustic
platform" for other applications.
"Our ability to suppress bubble build-up on the electrodes and rapidly
remove them through high-frequency vibrations represents a major
advance for electrode conductivity and stability. With our method, we
can potentially improve the conversion efficiency leading to a
net-positive energy saving of 27 percent," said Yeo from RMIT’s School
of Engineering.
However, integrating the sound-wave innovation with current
electrolyzers to scale up the work is a challenge the team needs to
work on.
Study Abstract:
A novel strategy utilizing high-frequency (10 MHz) hybrid sound waves
to dramatically enhance hydrogen evolution reactions (HER) in
notoriously difficult neutral electrolytes by modifying their network
coordination state is presented. Herein, the practical limitations
associated with existing electrolyzer technology is addressed,
including the need for highly corrosive electrolytes and expensive
electrocatalysts, by redefining conceptually-poor hydrogen
electrocatalysts in neutral electrolytes. The improvement in HER
performance is attributed to the unique capability of the intense
local electromechanical coupling arising from the acoustic-forcing to
‘frustrate’ the tetrahedrally-coordinated hydrogen bond network of
water molecules at the electrode–electrolyte interface, resulting in
the generation of a high concentration of “free” water molecules that
are more readily able to access catalytic sites on the unmodified
polycrystalline electrode. Together with the other synergistic effects
that accompany the acoustic excitation (e.g., hydronium ion
generation, convective relaxation of diffusion mass transfer
limitations, and prevention of bubble build-up and their removal from
the electrode), the resultant overpotential reduction of 1.4 V at −100
mA cm−2 and corresponding 14-fold increase in current density,
together with a net-positive energy saving of 27.3%, showcases the
potential of the technology as a scalable platform for effectively
enhancing the efficiency of green hydrogen production.
Green Play Ammonia™, Yielder® NFuel Energy.
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