Researchers at the University of Sydney have developed a sunlight-powered method to produce clean hydrogen from both freshwater and seawater using liquid metals.
The process avoids several long-standing barriers in green hydrogen production, including the need for purified water and high energy inputs.
The technique relies on liquid gallium, a metal with a low melting point, to extract hydrogen directly from water when exposed to light.
By using sunlight or artificial light, the method enables hydrogen generation without external electricity or complex infrastructure.
Hydrogen has long been seen as a promising clean fuel for industries ranging from transport and energy to manufacturing and agriculture.
However, producing green hydrogen at scale has remained expensive and inefficient, largely due to the energy required to split water molecules and the reliance on purified water sources.
The new approach allows hydrogen to be harvested from readily available water sources, including seawater, while maintaining competitive efficiency.
Lead author and PhD candidate Luis Campos said, “We now have a way of extracting sustainable hydrogen, using seawater, which is easily accessible while relying solely on light for green hydrogen production.”
At the core of the system is gallium, a metal that becomes liquid slightly above room temperature. When gallium particles are suspended in water and exposed to light, they undergo a surface reaction that releases hydrogen.
The metal reacts with water to form gallium oxyhydroxide while freeing hydrogen molecules.
Senior researcher Professor Kourosh Kalantar-Zadeh from the School of Chemical and Biomolecular Engineering said the work demonstrates the untapped chemical potential of liquid metals.
“For the first proof-of-concept, we consider the efficiency of this technology to be highly competitive,” he said.
The team achieved a maximum efficiency of 12.9 percent and is now working to improve it for commercial use.
Unlike conventional water-splitting methods such as electrolysis, the gallium-based process does not require purified water or expensive catalysts. It can operate with both freshwater and seawater, reducing cost and complexity.
This makes the system attractive for large-scale deployment, particularly in coastal or water-scarce regions.
The process is also circular. After hydrogen is released, the gallium oxyhydroxide formed during the reaction can be converted back into gallium and reused.
“After we extract hydrogen, the gallium oxyhydroxide can also be reduced back into gallium and reused for future hydrogen production, which we term a circular process,” Professor Kalantar-Zadeh said.
Built for scalable hydrogen
The researchers note that liquid gallium has rarely been explored for hydrogen production despite its unusual properties.
At room temperature, it appears solid, but it melts at near body temperature. In water and under light, its normally non-reactive surface begins to oxidize, triggering hydrogen release.
“Galiium has not been explored before as a way to produce hydrogen at high rates when in contact with water – such a simple observation that was ignored previously,” Professor Kalantar-Zadeh said.
Project co-lead Dr. Francois Allioux highlighted the broader implications of the work, saying, “Hydrogen offers a clean energy solution for a sustainable future and could play a pivotal role in Australia’s international advantage in a hydrogen economy.”
The team is now focused on increasing efficiency and building a mid-scale reactor to test real-world performance. If successful, the technology could offer a practical and scalable route to green hydrogen using abundant water and sunlight.
The study was published in Nature Communications.
