Researchers at the University of Cambridge demonstrated that gas that is currently produced from fossil fuels can instead be made by an ‘artificial leaf’ that uses only sunlight, carbon dioxide and water, and which could eventually be used to develop a sustainable liquid fuel alternative to petrol.
Rather than running on fossil fuels, the artificial leaf is powered by sunlight, although it still works efficiently on cloudy days. And unlike the current industrial processes for producing gas, the leaf does not release any additional carbon dioxide into the atmosphere.
This gas – called syngas – is currently made from a mixture of hydrogen and carbon monoxide, and is used to produce a range of commodities, such as fuels, pharmaceuticals, plastics and fertilisers.
“You may not have heard of syngas itself but every day, you consume products that were created using it. Being able to produce it sustainably would be a critical step in closing the global carbon cycle and establishing a sustainable chemical and fuel industry,” said senior author Professor Erwin Reisner from Cambridge’s Department of Chemistry, who has spent seven years working towards this goal.
The device Reisner and his colleagues produced is inspired by photosynthesis — the natural process by which plants use the energy from sunlight to turn carbon dioxide into food.
On the artificial leaf, two light absorbers, similar to the molecules in plants that harvest sunlight, are combined with a catalyst made from the naturally abundant element cobalt.
When the device is immersed in water, one light absorber uses the catalyst to produce oxygen. The other carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen, forming the syngas mixture.
As an added bonus, the researchers discovered that their light absorbers work even under the low levels of sunlight on a rainy or overcast day.
“This means you are not limited to using this technology just in warm countries, or only operating the process during the summer months,” said PhD student Virgil Andrei, first author of the paper. “You could use it from dawn until dusk, anywhere in the world.”
The team is now looking at ways to use their technology to produce a sustainable liquid fuel alternative to petrol.
“What we’d like to do next, instead of first making syngas and then converting it into liquid fuel, is to make the liquid fuel in one step from carbon dioxide and water. There is a major demand for liquid fuels to power heavy transport, shipping and aviation sustainably,” said Reisner.