Converting seawater into hydrogen using only sunlight

Hydrogen has a central role to play in the green energy transition, and Australia’s Hydrogen Strategy aims to place us at the forefront of the hydrogen economy. Now, an efficient catalyst that converts seawater into hydrogen using only sunlight could help enable this transition.

Challenge

Traditionally, hydrogen production uses electricity to break water molecules apart into hydrogen and oxygen. This is normally done using a source of fresh water. As freshwater resources become increasingly scarce, however, seawater presents an attractive alternative – if it can be effectively harnessed. Furthermore, approaches that eliminate the need for electricity and instead rely on catalysts could significantly enhance the sustainability and energy efficiency of hydrogen production.

RESEARCH

The researchers, led by Prof. Zongyou Yin at the Australian National University, in collaboration with experts at our UNSW Sydney facility have met these challenges. They designed and constructed unique and intricate catalyst nanoparticles consisting of copper spheres coated with a layer of nitrogen and carbon that also contains dispersed single atoms of cobalt. Sunlight interacts with the particles to make them very reactive and efficient at splitting water into hydrogen and oxygen. These particles don’t need the rare and expensive precious metals that many other approaches depend on and are also exceptionally stable in the long term.

The superior performance of these unique catalytic nanoparticles is due to two key factors. Firstly, the enhancement of the reaction by sunlight. Secondly, the reaction is further enhanced by the salts in the seawater.

The efficiency of the catalysts relies on the atomic configuration and interactions between the copper and the cobalt at the nanoscale. Accurate high-resolution imaging and elemental analysis were essential to confirm the composition and to visualise the structure of the nanoparticles. Amongst a suite of analytical techniques, the team used the atomic-scale transmission electron microscope at our UNSW Sydney facility, the Electron Microscope Unit.

Atomic-scale transmission electron microscope image showing the crystal structure of the copper core of the nanoparticles surrounded by a halo of the non-crystalline carbon–nitrogen–cobalt shell

Impact

These catalytic nanoparticles have the potential to be translated into a sustainable technology to enable the production of green hydrogen from just seawater and sunlight.

Z. Sun et al., Advanced Materials 2025
DOI: 10.1002/adma.202406088