22nd October 2019

The artificial leaf that can produce syngas

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Researchers at Cambridge University have demonstrated how an artificial leaf can make a gas that is currently produced from fossil fuels.

Syngas is currently widely used to produce a range of products including fuels, plastics, pharmaceuticals and fertilisers but could be produced more sustainably, according to the researchers.

Using only sunlight, carbon dioxide and water to produce the gas, the carbon-neutral leaf could eventually be used to develop a sustainable liquid fuel alternative to petrol.

The carbon-neutral device is powered by sunlight (but still works on cloudy and overcast days) without releasing any additional carbon dioxide into the atmosphere, unlike the current industrial processes for producing syngas, which is currently made from a mixture of hydrogen and carbon monoxide.

Professor Erwin Reisner, senior author from Cambridge’s Department of Chemistry, has spent seven years working towards this achievement, which was inspired by photosynthesis.

He said: “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,”

Two light absorbers on the artificial leaf (similar to plant molecules that harvest sunlight) are combined with a catalyst made from cobalt.

When immersed in water, one light absorber uses the catalyst to produce oxygen, while the other carries out the chemical reaction that reduces carbon dioxide and water into carbon monoxide and hydrogen, forming the syngas mixture.

Because the light absorbers work even on overcast days, PhD student Virgil Andrei, first author of the paper, said: “This means you are not limited to using this technology just in warm countries, or only operating the process during the summer months.

“You could use it from dawn until dusk, anywhere in the world.”

The research was carried out in the University’s Department of Chemistry and was co-funded by the Austrian government and the Austrian petrochemical company OMV, which aims to make its business more sustainable. It was also funded by the Winton Programme for the Physics of Sustainability, the Biotechnology and Biological Sciences Research Council, and the Engineering and Physical Sciences Research Council.

Michael-Dieter Ulbrich, senior advisor at OMV, said: “The team’s fundamental research to produce syngas as the basis for liquid fuel in a carbon neutral way is ground-breaking.”

The team is now investigating ways of using the pioneering technology to produce a sustainable liquid fuel alternative to petrol.

Professor Reisner said the development of synthetic petrol is vital, despite great advances being made in generating electricity from renewable energy sources, including wind power and photovoltaics (PV), as electricity can currently only satisfy about a quarter of our total global energy demand.

Virgil Andrei added: “We are aiming at sustainably creating products such as ethanol, which can readily be used as a fuel.

“It’s challenging to produce it in one step from sunlight using the carbon dioxide reduction reaction. But we are confident that we are going in the right direction, and that we have the right catalysts, so we believe we will be able to produce a device that can demonstrate this process in the near future.”