Scientists in Cambridge Produce an Artificial Leaf that Converts CO2 into Liquid Fuels

Category Technology

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Scientists from the University of Cambridge have developed an 'artificial leaf' powered by sunlight that converts CO2 and water into liquid fuels such as ethanol and propanol. These fuels have a high energy density and can be easily transported or stored, and are completely renewable with zero-carbon emissions. This innovation eliminates the intermediary step of producing syngas, making the technology more practical and paving the way for a sustainable future.

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University of Cambridge scientists have developed an ‘artificial leaf’ that, powered by sunlight, converts CO2 and water into ethanol and propanol. This innovation eliminates the intermediary step of producing syngas, making the technology more practical and paving the way for a sustainable, zero-carbon emission future.

Researchers have developed a solar-powered technology that converts carbon dioxide and water into liquid fuels that can be added directly to a car’s engine as drop-in fuel.

The catalyst used within the artificial leaf is a combination of copper and palladium.

The researchers, from the University of Cambridge, harnessed the power of photosynthesis to convert CO2, water, and sunlight into multicarbon fuels – ethanol and propanol – in a single step. These fuels have a high energy density and can be easily stored or transported.

Unlike fossil fuels, these solar fuels produce net zero carbon emissions and completely renewable, and unlike most bioethanol, they do not divert any agricultural land away from food production.

The artificial leaves are able to produce more complex chemicals than those produced by an electrical current.

While the technology is still at laboratory scale, the researchers say their ‘artificial leaves’ are an important step in the transition away from a fossil fuel-based economy. The results are reported in the journal Nature Energy.

Bioethanol is touted as a cleaner alternative to petrol, since it is made from plants instead of fossil fuels. Most cars and trucks on the road today run on petrol containing up to 10% ethanol (E10 fuel). The United States is the world’s largest bioethanol producer: according to the U.S. Department of Agriculture, almost 45% of all corn grown in the US is used for ethanol production.

The fuels produced by this process are high energy density.

"Biofuels like ethanol are a controversial technology, not least because they take up agricultural land that could be used to grow food instead," said Professor Erwin Reisner, who led the research.

For several years, Reisner’s research group, based in the Yusuf Hamied Department of Chemistry, has been developing sustainable, zero-carbon fuels inspired by photosynthesis – the process by which plants convert sunlight into food – using artificial leaves.

The process does not require an intermediary step of producing syngas.

To date, these artificial leaves have only been able to make simple chemicals, such as syngas, a mixture of hydrogen and carbon monoxide that is used to produce fuels, pharmaceuticals, plastics, and fertilizers. But to make the technology more practical, it would need to be able to produce more complex chemicals directly in a single solar-powered step.

Now, the artificial leaf can directly produce clean ethanol and propanol without the need for the intermediary step of producing syngas.

The fuels produced are entirely renewable and zero-carbon emissions.

The researchers developed a copper and palladium-based catalyst. The catalyst was optimized in a way that allowed the artificial leaf to produce more complex chemicals, specifically the multicarbon alcohols ethanol, and n-propanol. Both alcohols are high energy density fuels that can be easily transported and stored.

Other scientists have been able to produce similar chemicals using electrical power, but this is the first time that such complex chemicals have been produced with an artificial leaf using only the energy from the Sun.

Biofuels are often controversial due to taking up agricultural land for fuel production instead of food production.

"Shining sunlight on the artificial leaves and getting liquid fuel from carbon dioxide and water is an amazing bit of chemistry," said Dr Motiar Rahaman, the paper’s first author. "Normally, when you try to convert CO2 into another chemical product using power, you usually get energy back in the form of heat, but, with our technology, that power is converted into a fuel directly." .

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