Bombarding water with sound waves during electrolysis releases 14 times more hydrogen than when operating in silence, according to new research published in the scientific journal Advanced Energy Materials.
The high-frequency vibrations will also enable cheaper catalyst and electrode materials to be used, rather than platinum or iridium, thus reducing the potential cost of electrolyser production, the paper explains.
“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,” said co-author Yemima Ehrnst, a nanophysicist at RMIT University in Melbourne.
However, due to the amount of electricity required to produce the sound waves, the overall energy savings per unit of hydrogen amounted to only 27.3% — which is nevertheless a huge improvement on existing technology.
The increased H2 yield is attributed to the sound waves “frustrating” the bonds between water molecules on the surface of an electrode made from polycrystalline gold, “resulting in the generation of a high concentration of ‘free’ water molecules that are more readily able to access catalytic sites”.
Other “synergistic” impacts of the sound waves , including the prevention of bubble build-up on the electrode, add to the effectiveness of the “acoustic forcing”, which has the potential to enhance the efficiency of green hydrogen production.
The team is now looking at how to integrate its findings with existing electrolysers.
“We are keen to collaborate with industry partners to boost and complement their existing electrolyser technology and integrate into existing processes and systems," says Professor Leslie Yeo, from RMIT, one of the paper’s co-authors.
“With our method, we can potentially improve the conversion efficiency leading to a net-positive energy saving of 27%”.
Project leader Amgad Rezk, an associate professor at RMIT, says electrode materials are among the biggest challenges of electrolysis.
“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,” he said.
“As water is not a corrosive electrolyte, we can use much cheaper electrode materials such as silver.”
Another recent study, published in Nature by researchers from the University of Singapore, showed that electrolysis could be boosted by light.
An accidental power cut in a laboratory’s ceiling lights during an electrolysis experiment showed a drastically decreased performance, and subsequent research found that light could boost the energy efficiency of the process under certain conditions.
But it was unclear how much more efficient the light made the electrolysis process.
The University of Singapore team has not responded to questions from Hydrogen Insight.
