Because it works with any open water source and doesn't require external power, the device could be used in resource-limited or remote places.

Photocatalytic water splitting converts sunlight directly into storable hydrogen but often requires pure water and land for plant installation, while generating unusable waste heat. With water being a precious resource, a photocatalytic device that uses any untreated water source, such as a river, sea, water reservoir or industrial waste water, would be a more sustainable option.

So researchers from the University of Cambridge, inspired by the process of photosynthesis, created a solar-powered device capable of producing clean hydrogen fuel and clean drinking water simultaneously from polluted water or seawater.

"Bringing together solar fuels production and water production in a single device is tricky," said Chanon Pornrungroj, the study's lead author. "Solar-driven water splitting, where water molecules are broken down into hydrogen and oxygen, need to start with totally pure water because any contaminants can poison the catalyst or cause unwanted chemical side-reactions."

The researchers wanted to mimic a plant's ability to photosynthesize, but unlike previous devices that produced green hydrogen fuel from clean water sources, they wanted their device to use contaminated water, making it usable in regions where clean water is hard to find.

"In remote or developing regions, where clean water is relatively scarce and the infrastructure necessary for water purification is not readily available, water splitting is extremely difficult," said Ariffin Mohamad Annuar, a study co-author. "A device that could work using contaminated water could solve two problems at once: it could split water to make clean fuel, and it could make clean drinking water."