RESEARCHERS at the University of Sydney have developed a photothermal method for producing hydrogen from freshwater and seawater using liquid gallium, with the potential for circular operation through metal regeneration.
Published in Nature Communications, the study describes how exposure to light thermally heats liquid gallium droplets, triggering oxidation at the metal–water interface. The reaction produces hydrogen alongside gallium oxyhydroxide.
Light plays a dual role in the process. In addition to heating the metal, it disrupts the oxide layer that naturally forms on gallium’s surface, enabling sustained interaction between water molecules and the liquid metal.
Unlike conventional electrolysis, the approach does not require purified water and operates without an external electrical input during hydrogen generation, potentially avoiding the energy and cost associated with desalination and water treatment.
Crucially, the gallium oxyhydroxide byproduct can be electrochemically reduced back to metallic gallium, enabling regeneration of the material and what the researchers describe as a “circular” hydrogen production route.
PhD candidate Luis Campos, who led the study, 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.”
The team are now investigating scaleup, including development of a mid-scale reactor to evaluate efficiency and materials stability under continuous operation.
Senior researcher Kourosh Kalantar-Zadeh added: “There is a global need to commercialise a highly efficient method for producing green hydrogen. Our process is efficient and easy to scale up.”
