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Electric vehicles are heralded as the future of zero-emission transportation, but the ultimate eco-friendly car could run on sunshine.
Researchers have created an “artificial leaf” that uses sunlight to convert water and carbon dioxide into low-emission fuels — ethanol and propanol.
If this sounds familiar, the artificial leaf mimics photosynthesis, the famous process plants use to create their energy.
In the lab, the experts immersed the leaf in CO2-infused water before shining light on it to kick-start the reaction and create the green fuels.
But in the future, cars could be built with the technology to absorb surrounding sunlight, CO2 and water vapor in the air and produce the fuels along the way.
Electric vehicles are heralded as the future of zero-emission transportation, but the ultimate eco-friendly car could run on sunshine
Researchers have created an “artificial leaf” that uses sunlight to convert water and carbon dioxide into low-emission fuels — ethanol and propanol. The artificial leaf is shown here attached to a metal bar. In the future, it could be part of a car’s device to produce clean fuel on the go
The technology is described in a new study led by researchers at the University of Cambridge and published in the journal Nature Energy.
“Shining sunlight on the artificial leaves and getting liquid fuel from carbon dioxide and water is an amazing piece of chemistry,” said study co-author Dr Motiar Rahaman.
‘In this work, we developed an artificial foliar device to generate multicarbon alcohols from CO2 and water using sunlight as the only energy source.’
Researchers made their ‘artificial sheet’ from several layers including copper, glass, silver and graphite.
The artificial leaf contains light-absorbing substances – comparable to the molecules in plants that absorb sunlight – that are combined with a catalyst.
This catalyst (which is related to chlorophyll, the catalyst for photosynthesis in a real leaf) is made of two elements, copper and palladium.
In the presence of sunlight, the catalyst converts CO2 into ethanol and propanol, and the water into oxygen.
“The alcohol products can be taken out of the reaction medium and then used in a car,” Dr. Rahaman to MailOnline.
While the technology is still at the lab scale, the scientists say their “artificial leaves” are an important step in the transition from fossil fuels currently used in cars, namely petroleum.
Pictured is a photoreactor with the artificial leaf and CO2-infused water. This is a scaled-down lab version of what the technology could look like. In the future, cars could be built to absorb the surrounding sunlight, CO2 and water vapor in the air and produce fuel along the way
The Cambridge researchers made their ‘artificial sheet’ from several layers including copper, glass, silver and graphite, as well as copper and palladium for the catalyst
Ethanol is already used as a clean fuel in cars and is usually made from biomass such as corn or sugar cane.
It is touted as a greener alternative to gasoline because it is made from plants rather than fossil fuels.
Many cars and trucks on the road today run on gasoline containing up to 10 percent ethanol (sold at gas stations as E10 fuel).
One problem, however, is that ethanol production takes up farmland that could be used to grow food instead.
According to the US Department of Agriculture, nearly 45 percent of all corn grown in the US is used for ethanol production.
And the more demand for this environmentally friendly ethanol grows, the more land is needed.
Fortunately, the Cambridge team’s technology offers an alternative production method to ethanol.
In the future, the lead could be part of a car’s device to produce clean fuel along the way if it could pull water and CO2 from the surrounding air while exposed to sunlight.
However, the team warns that the device is only a proof of concept with “modest efficiency” at this point.
“While there is still work to be done, we have shown what these artificial leaves are capable of,” said study co-author Professor Erwin Reisner at Cambridge, who led the research.
“It’s important to show that we can go beyond the simplest molecules and make things that are immediately usable as we move away from fossil fuels.”
In 2019, the Cambridge team described using their artificial leaf technology to produce synthetic gas or ‘syngas’ – a mixture of hydrogen and carbon monoxide used to produce fuels, pharmaceuticals, plastics and fertilizers.
Currently, cars and trucks on the road run on gasoline containing up to 10 percent ethanol (known as E10 fuel)
But now the artificial leaf can directly produce clean ethanol and propanol without the intermediate step of producing syngas.
In addition, ethanol and propanol are environmentally friendly fuels with a high energy density that are easy to store or transport.
‘Normally you almost always get carbon monoxide or syngas when you try to convert CO2 into another chemical product using an artificial foliar device,’ says Dr Rahaman.
‘But here we have been able to produce a practical liquid fuel using only the power of the sun.
“It’s exciting progress that opens up entirely new avenues in our work.”
The researchers are now working on improving the light absorbers, so that they can better absorb sunlight, and the catalyst, so that it can convert more sunlight into fuel.
Further work will also be needed to make the device scalable so that it can produce large amounts of fuel – although it’s unclear how much this would cost.