̽��ֱ�� of Cambridge - Sayan Kar

Solar-powered device captures carbon dioxide from air to make sustainable fuel

sc604 — Thu, 13 Feb 2025 10:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, say their solar-powered reactor could be used to make fuel to power cars and planes, or the many chemicals and pharmaceuticals products we rely on. It could also be used to generate fuel in remote or off-grid locations.

Unlike most carbon capture technologies, the reactor developed by the Cambridge researchers does not require fossil-fuel-based power, or the transport and storage of carbon dioxide, but instead converts atmospheric CO2 into something useful using sunlight. ̽��ֱ��results are reported in the journal Nature Energy.

Carbon Capture and Storage (CCS) has been touted as a possible solution to the climate crisis, and has recently received £22bn in funding from the UK government. However, CCS is energy-intensive and there are concerns about the long-term safety of storing pressurised CO2 deep underground, although safety studies are currently being carried out.

“Aside from the expense and the energy intensity, CCS provides an excuse to carry on burning fossil fuels, which is what caused the climate crisis in the first place,” said Professor Erwin Reisner, who led the research. “CCS is also a non-circular process, since the pressurised CO2 is, at best, stored underground indefinitely, where it’s of no use to anyone.”

“What if instead of pumping the carbon dioxide underground, we made something useful from it?” said first author Dr Sayan Kar from Cambridge’s Yusuf Hamied Department of Chemistry. “CO2 is a harmful greenhouse gas, but it can also be turned into useful chemicals without contributing to global warming.”

̽��ֱ��focus of Reisner’s research group is the development of devices that convert waste, water and air into practical fuels and chemicals. These devices take their inspiration from photosynthesis: the process by which plants convert sunlight into food. ̽��ֱ��devices don’t use any outside power: no cables, no batteries – all they need is the power of the sun.

̽��ֱ��team’s newest system takes CO2 directly from the air and converts it into syngas: a key intermediate in the production of many chemicals and pharmaceuticals. ̽��ֱ��researchers say their approach, which does not require any transportation or storage, is much easier to scale up than earlier solar-powered devices.

̽��ֱ��device, a solar-powered flow reactor, uses specialised filters to grab CO2 from the air at night, like how a sponge soaks up water. When the sun comes out, the sunlight heats up the captured CO2, absorbing infrared radiation and a semiconductor powder absorbs the ultraviolet radiation to start a chemical reaction that converts the captured CO2 into solar syngas. A mirror on the reactor concentrates the sunlight, making the process more efficient.

̽��ֱ��researchers are currently working on converting the solar syngas into liquid fuels, which could be used to power cars, planes and more – without adding more CO2 to the atmosphere.

“If we made these devices at scale, they could solve two problems at once: removing CO2 from the atmosphere and creating a clean alternative to fossil fuels,” said Kar. “CO2 is seen as a harmful waste product, but it is also an opportunity.”

̽��ֱ��researchers say that a particularly promising opportunity is in the chemical and pharmaceutical sector, where syngas can be converted into many of the products we rely on every day, without contributing to climate change. They are building a larger scale version of the reactor and hope to begin tests in the spring.

If scaled up, the researchers say their reactor could be used in a decentralised way, so that individuals could theoretically generate their own fuel, which would be useful in remote or off-grid locations.

“Instead of continuing to dig up and burn fossil fuels to produce the products we have come to rely on, we can get all the CO2 we need directly from the air and reuse it,” said Reisner. “We can build a circular, sustainable economy – if we have the political will to do it.”

̽��ֱ��technology is being commercialised with the support of Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm. ̽��ֱ��research was supported in part by UK Research and Innovation (UKRI), the European Research Council, the Royal Academy of Engineering, and the Cambridge Trust. Erwin Reisner is a Fellow of St John’s College, Cambridge.

Reference:
Sayan Kar et al. ‘Direct air capture of CO2 for solar fuels production in flow.’ Nature Energy (2025). DOI: 10.1038/s41560-025-01714-y

For more information on energy-related research in Cambridge, please visit the Energy IRC, which brings together Cambridge’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

Researchers have developed a reactor that pulls carbon dioxide directly from the air and converts it into sustainable fuel, using sunlight as the power source.

We can build a circular, sustainable economy – if we have the political will to do it

Erwin Reisner

Sayan Kar

Solar-powered flow reactor

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Clean, sustainable fuels made ‘from thin air’ and plastic waste

sc604 — Mon, 19 Jun 2023 15:15:53 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, developed a solar-powered reactor that converts captured CO2 and plastic waste into sustainable fuels and other valuable chemical products. In tests, CO2 was converted into syngas, a key building block for sustainable liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry.

Unlike earlier tests of their solar fuels technology however, the team took CO2 from real-world sources – such as industrial exhaust or the air itself. ̽��ֱ��researchers were able to capture and concentrate the CO2 and convert it into sustainable fuel.

Although improvements are needed before this technology can be used at an industrial scale, the results, reported in the journal Joule, represent another important step toward the production of clean fuels to power the economy, without the need for environmentally destructive oil and gas extraction.

For several years, Professor Erwin Reisner’s research group, based in the Yusuf Hamied Department of Chemistry, has been developing sustainable, net-zero carbon fuels inspired by photosynthesis – the process by which plants convert sunlight into food – using artificial leaves. These artificial leaves convert CO2 and water into fuels using just the power of the sun.

To date, their solar-driven experiments have used pure, concentrated CO2 from a cylinder, but for the technology to be of practical use, it needs to be able to actively capture CO2 from industrial processes, or directly from the air. However, since CO2 is just one of many types of molecules in the air we breathe, making this technology selective enough to convert highly diluted CO2 is a huge technical challenge.

“We’re not just interested in decarbonisation, but de-fossilisation – we need to completely eliminate fossil fuels in order to create a truly circular economy,” said Reisner. “In the medium term, this technology could help reduce carbon emissions by capturing them from industry and turning them into something useful, but ultimately, we need to cut fossil fuels out of the equation entirely and capture CO2 from the air.”

̽��ֱ��researchers took their inspiration from carbon capture and storage (CCS), where CO2 is captured and then pumped and stored underground.

“CCS is a technology that’s popular with the fossil fuel industry as a way to reduce carbon emissions while continuing oil and gas exploration,” said Reisner. “But if instead of carbon capture and storage, we had carbon capture and utilisation, we could make something useful from CO2 instead of burying it underground, with unknown long-term consequences, and eliminate the use of fossil fuels.”

̽��ֱ��researchers adapted their solar-driven technology so that it works with flue gas or directly from the air, converting CO2 and plastics into fuel and chemicals using only the power of the sun.

By bubbling air through the system containing an alkaline solution, the CO2 selectively gets trapped, and the other gases present in air, such as nitrogen and oxygen, harmlessly bubble out. This bubbling process allows the researchers to concentrate the CO2 from air in solution, making it easier to work with.

̽��ֱ��integrated system contains a photocathode and an anode. ̽��ֱ��system has two compartments: on one side is captured CO2 solution that gets converted into syngas, a simple fuel. On the other plastics are converted into useful chemicals using only sunlight.

“ ̽��ֱ��plastic component is an important trick to this system,” said co-first author Dr Motiar Rahaman. “Capturing and using CO2 from the air makes the chemistry more difficult. But, if we add plastic waste to the system, the plastic donates electrons to the CO2. ̽��ֱ��plastic breaks down to glycolic acid, which is widely used in the cosmetics industry, and the CO2 is converted into syngas, which is a simple fuel.”

“This solar-powered system takes two harmful waste products – plastic and carbon emissions – and converts them into something truly useful,” said co-first author Dr Sayan Kar.

“Instead of storing CO2 underground, like in CCS, we can capture it from the air and make clean fuel from it,” said Rahaman. “This way, we can cut out the fossil fuel industry from the process of fuel production, which can hopefully help us avoid climate destruction.”

“ ̽��ֱ��fact that we can effectively take CO2 from air and make something useful from it is special,” said Kar. “It’s satisfying to see that we can actually do it using only sunlight.”

̽��ֱ��scientists are currently working on a bench-top demonstrator device with improved efficiency and practicality to highlight the benefits of coupling direct air capture with CO2 utilisation as a path to a zero-carbon future.

̽��ֱ��research was supported in part by the Weizmann Institute of Science, the European Commission Marie Skłodowska-Curie Fellowship, the Winton Programme for the Physics of Sustainability, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Erwin Reisner is a Fellow and Motiar Rahaman is a Research Associate of St John’s College, Cambridge. Erwin Reisner leads the Cambridge Circular Plastics Centre (CirPlas), which aims to eliminate plastic waste by combining blue-sky thinking with practical measures.

Reference:
Sayan Kar, Motiar Rahaman et al. ‘Integrated Capture and Solar-driven Utilization of CO2 from Flue Gas and Air.’ Joule (2023). DOI: 10.1016/j.joule.2023.05.022

For more information on energy-related research in Cambridge, please visit Energy IRC, which brings together Cambridge’s research knowledge and expertise, in collaboration with global partners, to create solutions for a sustainable and resilient energy landscape for generations to come.

Researchers have demonstrated how carbon dioxide can be captured from industrial processes – or even directly from the air – and transformed into clean, sustainable fuels using just the energy from the sun.

We’re not just interested in decarbonisation, but de-fossilisation – we need to completely eliminate fossil fuels in order to create a truly circular economy

Erwin Reisner

Ariffin Mohamad Annuar

Carbon capture from air and its photoelectrochemical conversion into fuel with simultaneous waste plastic conversion into chemicals.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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