Artificial floating leaves produce fuel from the sun and water

Aug. 17 () –

Cambridge scientists presented in Nature floating “artificial leaves” that generate clean fuels from sunlight and water, and could work on a large scale in the sea.

The team has designed ultra-thin, flexible devices that are inspired by photosynthesis, the process by which plants convert sunlight into food. Because these low-cost, self-contained devices are light enough to float, could be used to generate a sustainable alternative to gasoline without taking up space on land.

Outdoor tests conducted with these lightweight sheets on the River Cam, near Cambridge landmarks such as the Bridge of Sighs, the Wren Library and King’s College Chapel, They showed that they can convert sunlight into fuel just as efficiently as plant leaves.

It is the first time that clean fuel has been generated in water and, if scaled up, the artificial leaves could be used in polluted waterways, in ports or even at sea, and could help reduce the global shipping industry’s dependence on fossil fuels.

While renewable energy technologies like wind and solar have become considerably cheaper and more widely available in recent years, for industries like shipping, decarbonizing is a much more difficult task. About 80% of world trade is transported by fossil fuel-powered cargo ships and yet the sector has received very little attention in debates about the climate crisis.

For several years, Professor Erwin Reisner’s research group in Cambridge has been working to tackle this problem by developing sustainable solutions for gasoline that are based on the principles of photosynthesis. In 2019, they developed an artificial leaf that makes syngas – a key intermediate in the production of many chemicals and pharmaceuticals – from sunlight, carbon dioxide and water.

The previous prototype generated fuel by combining two light absorbers with suitable catalysts. Nevertheless, it incorporated thick glass substrates and moisture-protective coatings, making the device bulky.

“Artificial leaves could substantially reduce the cost of sustainable fuel production, but because they are heavy and brittle, they are difficult to produce at scale and difficult to transport,” explains co-author Dr Virgil Andrei, from Cambridge’s Yusuf Hamied Department of Chemistry. from the article.

“We wanted to see how far we could reduce the materials used by these devices without affecting their performance Reisner, who led the investigation, explains. If we can reduce the materials enough to make them light enough to float, it will open up new possibilities for using these artificial leaves.”

For the new version of the artificial leaf, the researchers drew inspiration from the electronics industry, where miniaturization techniques have led to the creation of flexible smartphones and screens. revolutionizing the field.

The challenge for the Cambridge researchers was how to deposit the light absorbers on light substrates and protect them against water infiltration. To overcome these challenges, the team used thin-film metal oxides and materials known as perovskites, which can be coated onto flexible sheets of plastic and metal.

The devices were covered with micrometric, water-repellent carbon layers that prevented degradation by moisture. The result was a device that not only works, but looks like a real blade.

“This study demonstrates that artificial leaves are compatible with modern manufacturing techniques, representing a first step towards automation and scaling up solar fuel production,” Andrei says. “These leaves combine the advantages of most of solar fuel technologies, as they achieve the low weight of powder suspensions and the high performance of wired systems.”

Tests of the new artificial leaves showed that they can split water into hydrogen and oxygen, or reduce CO2 to syngas. Although further improvements will need to be made before they are ready for commercial applications, the researchers say this breakthrough opens up new avenues of work.

“Solar farms have become popular for electricity production; we envision similar farms for fuel synthesis,” Andrei says. They could supply coastal settlements, remote islands, cover industrial ponds or prevent the evaporation of water from irrigation canals.”

“Many renewable energy technologies, including solar fuel technologies, can take up a lot of space on land, so moving production to open water would mean that clean energy and land use are not in competition with each other,” Reisner continued. –.In theory, these devices could be rolled up and placed almost anywhere, in almost any country, which would also help energy security”.