A widely-used 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
gasoline.
University of Cambridge – October 21,
2019 -- The carbon-neutral device sets a new benchmark in the field of solar
fuels, after researchers at the University of Cambridge demonstrated that it can
directly produce the gas -- called syngas -- in a sustainable and simple way.
Rather than running on fossil fuels, the
artificial leaf is powered by sunlight, although it still works efficiently on
cloudy and overcast days. And unlike the current industrial processes for
producing syngas, the leaf does not release any additional carbon dioxide into
the atmosphere. The results are reported in the journal Nature Materials.
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 research was carried out in the
Christian Doppler Laboratory for Sustainable SynGas Chemistry in the
University's Department of Chemistry. It was co-funded by the Austrian
government and the Austrian petrochemical company OMV, which is looking for
ways to make its business more sustainable.
"OMV has been an avid supporter of
the Christian Doppler Laboratory for the past seven years. The team's
fundamental research to produce syngas as the basis for liquid fuel in a carbon
neutral way is ground-breaking," said Michael-Dieter Ulbrich, Senior
Advisor at OMV.
Other 'artificial leaf' devices have
also been developed, but these usually only produce hydrogen. The Cambridge
researchers say the reason they have been able to make theirs produce syngas
sustainably is thanks the combination of materials and catalysts they used.
These include state-of-the-art
perovskite light absorbers, which provide a high photovoltage and electrical
current to power the chemical reaction by which carbon dioxide is reduced to carbon
monoxide, in comparison to light absorbers made from silicon or dye-sensitised
materials. The researchers also used cobalt as their molecular catalyst,
instead of platinum or silver. Cobalt is not only lower-cost, but it is better
at producing carbon monoxide than other catalysts.
The team is now looking at ways to use
their technology to produce a sustainable liquid fuel alternative to petrol.
Syngas is already used as a building
block in the production of liquid fuels. "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," said Reisner, who
is also a Fellow of St John's College.
Although great advances are being made
in generating electricity from renewable energy sources such as wind power and
photovoltaics, Reisner says the development of synthetic petrol is vital, as
electricity can currently only satisfy about 25% of our total global energy
demand. "There is a major demand for liquid fuels to power heavy
transport, shipping and aviation sustainably," he said.
"We are aiming at sustainably
creating products such as ethanol, which can readily be used as a fuel,"
said Andrei. "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."
No comments:
Post a Comment