Dec 13, 2022 |
Good vibrations turbo charge green hydrogen production
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(Nanowerk News) Engineers in Melbourne have used sound waves to boost production of green hydrogen by 14 times, through electrolysis to split water.
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They say their invention offers a promising way to tap into a plentiful supply of cheap hydrogen fuel for transportation and other sectors, which could radically reduce carbon emissions and help fight climate change.
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By using high-frequency vibrations to “divide and conquer” individual water molecules during electrolysis, the team managed to split the water molecules to release 14 times more hydrogen compared with standard electrolysis techniques.
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Electrolysis involves electricity running through water with two electrodes to split water molecules into oxygen and hydrogen gases, which appear as bubbles. This process produces green hydrogen, which represents just a small fraction of hydrogen production globally due to the high energy required.
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Most hydrogen is produced from splitting natural gas, known as blue hydrogen, which emits greenhouse gases into the atmosphere.
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Associate Professor Amgad Rezk from RMIT University, who led the work, said the team’s innovation tackles big challenges for green hydrogen production.
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“One of the main challenges of electrolysis is the high cost of electrode materials used, such as platinum or iridium,” said Rezk from RMIT’s School of Engineering.
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“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.
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“As water is not a corrosive electrolyte, we can use much cheaper electrode materials such as silver.”
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The ability to use low-cost electrode materials and avoiding the use of highly corrosive electrolytes were gamechangers for lowering the costs of producing green hydrogen, Rezk said.
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The research is published in Advanced Energy Materials ("Acoustically-Induced Water Frustration for Enhanced Hydrogen Evolution Reaction in Neutral Electrolytes"). An Australian provisional patent application has been filed to protect the new technology.
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First author Yemima Ehrnst said the sound waves also prevented the build-up of hydrogen and oxygen bubbles on the electrodes, which greatly improved its conductivity and stability.
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“Electrode materials used in electrolysis suffer from hydrogen and oxygen gas build-up, forming a gas layer that minimises the electrodes’ activity and significantly reduces its performance,” said Ehrnst, a PhD researcher at RMIT’s School of Engineering.
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As part of their experiments the team measured the amount of hydrogen produced through electrolysis with and without sound waves from the electrical output.
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“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,” Ehrnst said.
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The potential applications of the team’s work
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Distinguished Professor Leslie Yeo, one of the lead senior researchers, said the team’s breakthrough opened the door to using this new acoustic platform for other applications, especially where bubble build-up on the electrodes was a challenge.
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“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,” said Yeo from RMIT’s School of Engineering.
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“With our method, we can potentially improve the conversion efficiency leading to a net-positive energy saving of 27%.”
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Next steps
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While the innovation is promising, the team needs to overcome challenges with integrating the sound-wave innovation with existing electrolysers to scale up the work.
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"We are keen to collaborate with industry partners to boost and complement their existing electrolyser technology and integrate into existing processes and systems," Yeo said.
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