Breakthrough device cleans dirty water and turns it into fuel

Scientists have built a breakthrough device that can clean dirty water and turn it into clean hydrogen fuel.

The “simple” device could be used in areas without resources or places where people live off the grid. And it is just one example of the many solutions that will be required to respond to pollution and give people access to both clean fuel and water, the researchers behind it say.

The system is inspired by photosynthesis, the process where plants turn light into food. But previous versions of those “artificial leaves” have required clean water sources – whereas the new device can be used with polluted water and even produce clean drinking water at the same time.

As such, scientists believe that it could help solve two problems at once: making green fuel and cleaning water so that it is ready to drink.

“Bringing together solar fuels production and water purification in a single device is tricky,” said Chanon Pornrungroj from the University of Cambridge, the paper’s co-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 system uses a carbon mesh to absorb light and heat, creating water vapour that is then turned into hydrogen for fuel by a photocatalyst. That carbon mesh also repels water, so that the system can float and its important parts can be kept from being damaged by water.

The device is also able to harness more of the Sun’s energy than previous examples, which have used only a small portion of the spectrum of light. The new system has a white layer on top to absorb UV rays, with the rest being used lower down to vaporise the water.

“This way, we’re making better use of the light – we get the vapour for hydrogen production, and the rest is water vapour,” said Dr Pornrungroj. “This way, we’re truly mimicking a real leaf, since we’ve now been able to incorporate the process of transpiration.”

The researchers behind the breakthrough noted that the system was simple to make, and was especially able to deal with very polluted water. As such, it could be a key way of working towards a sustainable future, they said – even though it is just a proof of concept for now.

“The climate crisis and issues around pollution and health are closely related, and developing an approach that could help address both would be a game-changer for so many people,” said Cambridge’s Erwin Reisner, who led the work.

The device is described in a new paper, ‘Hybrid photothermal-photocatalyst sheets for solar-driven overall water splitting coupled to water purification’, published in Nature Water today.