̽��ֱ�� of Cambridge - solar

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.

Yes

Tiny copper ‘flowers’ bloom on artificial leaves for clean fuel production

sc604 — Mon, 03 Feb 2025 09:28:45 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge and the ̽��ֱ�� of California, Berkeley, developed a practical way to make hydrocarbons – molecules made of carbon and hydrogen – powered solely by the sun.

̽��ֱ��device they developed combines a light absorbing ‘leaf’ made from a high-efficiency solar cell material called perovskite, with a copper nanoflower catalyst, to convert carbon dioxide into useful molecules. Unlike most metal catalysts, which can only convert CO₂ into single-carbon molecules, the copper flowers enable the formation of more complex hydrocarbons with two carbon atoms, such as ethane and ethylene — key building blocks for liquid fuels, chemicals and plastics.

Almost all hydrocarbons currently stem from fossil fuels, but the method developed by the Cambridge-Berkeley team results in clean chemicals and fuels made from CO2, water and glycerol – a common organic compound – without any additional carbon emissions. ̽��ֱ��results are reported in the journal Nature Catalysis.

̽��ֱ��study builds on the team’s earlier work on artificial leaves, which take their inspiration from photosynthesis: the process by which plants convert sunlight into food. “We wanted to go beyond basic carbon dioxide reduction and produce more complex hydrocarbons, but that requires significantly more energy,” said Dr Virgil Andrei from Cambridge’s Yusuf Hamied Department of Chemistry, the study’s lead author.

Andrei, a Research Fellow of St John’s College, Cambridge, carried out the work as part of the Winton Cambridge-Kavli ENSI Exchange programme in the lab of Professor Peidong Yang at ̽��ֱ�� of California, Berkeley.

By coupling a perovskite light absorber with the copper nanoflower catalyst, the team was able to produce more complex hydrocarbons. To further improve efficiency and overcome the energy limits of splitting water, the team added silicon nanowire electrodes that can oxidise glycerol instead. This new platform produces hydrocarbons much more effectively — 200 times better than earlier systems for splitting water and carbon dioxide.

̽��ֱ��reaction not only boosts CO₂ reduction performance, but also produces high-value chemicals such as glycerate, lactate, and formate, which have applications in pharmaceuticals, cosmetics, and chemical synthesis.

“Glycerol is typically considered waste, but here it plays a crucial role in improving the reaction rate,” said Andrei. “This demonstrates we can apply our platform to a wide range of chemical processes beyond just waste conversion. By carefully designing the catalyst’s surface area, we can influence what products we generate, making the process more selective.”

While current CO₂-to-hydrocarbon selectivity remains around 10%, the researchers are optimistic about improving catalyst design to increase efficiency. ̽��ֱ��team envisions applying their platform to even more complex organic reactions, opening doors for innovation in sustainable chemical production. With continued improvements, this research could accelerate the transition to a circular, carbon-neutral economy.

“This project is an excellent example of how global research partnerships can lead to impactful scientific advancements,” said Andrei. “By combining expertise from Cambridge and Berkeley, we’ve developed a system that may reshape the way we produce fuels and valuable chemicals sustainably.”

̽��ֱ��research was supported in part by the Winton Programme for the Physics of Sustainability, St John’s College, the US Department of Energy, the European Research Council, and UK Research and Innovation (UKRI).

Reference:
Virgil Andrei et al. ‘Perovskite-driven solar C2 hydrocarbon synthesis from CO2.’ Nature Catalysis (2025). DOI: 10.1038/s41929-025-01292-y

Tiny copper ‘nano-flowers’ have been attached to an artificial leaf to produce clean fuels and chemicals that are the backbone of modern energy and manufacturing.

Virgil Andrei

Solar fuel generator

Yes

Solar-powered device produces clean water and clean fuel at the same time

sc604 — Mon, 13 Nov 2023 16:21:43 +0000

̽��ֱ��device, developed by researchers at the ̽��ֱ�� of Cambridge, could be useful in resource-limited or off-grid environments, since it works with any open water source and does not require any outside power.

It takes its inspiration from photosynthesis, the process by which plants convert sunlight into food. However, unlike earlier versions of the ‘artificial leaf’, which could produce green hydrogen fuel from clean water sources, this new device operates from polluted or seawater sources and can produce clean drinking water at the same time.

Tests of the device showed it was able to produce clean water from highly polluted water, seawater, and even from the River Cam in central Cambridge. ̽��ֱ��results are reported in the journal Nature Water.

“Bringing together solar fuels production and water purification in a single device is tricky,” said Dr Chanon Pornrungroj from Cambridge’s Yusuf Hamied Department of Chemistry, the paper’s co-lead author. “Solar-driven water splitting, where water molecules are broken down into hydrogen and oxygen, need to start with totally pure water because any contaminants can poison the catalyst or cause unwanted chemical side-reactions.”

“In remote or developing regions, where clean water is relatively scarce and the infrastructure necessary for water purification is not readily available, water splitting is extremely difficult,” said co-lead author Ariffin Mohamad Annuar. “A device that could work using contaminated water could solve two problems at once: it could split water to make clean fuel, and it could make clean drinking water.”

Pornrungroj and Mohamad Annuar, who are both members of Professor Erwin Reisner’s research group, came up with a design that did just that. They deposited a photocatalyst on a nanostructured carbon mesh that is a good absorber of both light and heat, generating the water vapour used by the photocatalyst to create hydrogen. ̽��ֱ��porous carbon mesh, treated to repel water, served both to help the photocatalyst float and to keep it away from the water below, so that contaminants do not interfere with its functionality.

In addition, the new device uses more of the Sun’s energy. “ ̽��ֱ��light-driven process for making solar fuels only uses a small portion of the solar spectrum – there’s a whole lot of the spectrum that goes unused,” said Mohamad Annuar.

̽��ֱ��team used a white, UV-absorbing layer on top of the floating device for hydrogen production via water splitting. ̽��ֱ��rest of the light in the solar spectrum is transmitted to the bottom of the device, which vaporises the water.

“This way, we’re making better use of the light – we get the vapour for hydrogen production, and the rest is water vapour,” said Pornrungroj. “This way, we’re truly mimicking a real leaf, since we’ve now been able to incorporate the process of transpiration.”

A device that can make clean fuel and clean water at once using solar power alone could help address the energy and the water crises facing so many parts of the world. For example, the indoor air pollution caused by cooking with ‘dirty’ fuels, such as kerosene, is responsible for more than three million deaths annually, according to the World Health Organization. Cooking with green hydrogen instead could help reduce that number significantly. And 1.8 billion people worldwide still lack safe drinking water at home.

“It’s such a simple design as well: in just a few steps, we can build a device that works well on water from a wide variety of sources,” said Mohamad Annuar.

“It’s so tolerant of pollutants, and the floating design allows the substrate to work in very cloudy or muddy water,” said Pornrungroj. “It’s a highly versatile system.”

“Our device is still a proof of principle, but these are the sorts of solutions we will need if we’re going to develop a truly circular economy and sustainable future,” said Reisner, who led the research. “ ̽��ֱ��climate crisis and issues around pollution and health are closely related, and developing an approach that could help address both would be a game-changer for so many people.”

̽��ֱ��research was supported in part by the European Commission’s Horizon 2020 programme, ̽��ֱ��European Research Council, the Cambridge Trust, the Petronas Education Sponsorship Programme, and the Winton Programme for the Physics of Sustainability. Erwin Reisner is a Fellow of St John’s College. Chanon Pornrungroj is a member of Darwin College, and Ariffin Mohamad Annuar is a member of Clare College.

Reference:
Chanon Pornrungroj, Ariffin Bin Mohamad Annuar et al. ‘Hybrid photothermal-photocatalyst sheets for solar-driven overall water splitting coupled to water purification.’ Nature Water (2023). DOI: 10.1038/s44221-023-00139-9

A floating, solar-powered device that can turn contaminated water or seawater into clean hydrogen fuel and purified water, anywhere in the world, has been developed by researchers.

These are the sorts of solutions we will need to develop a truly circular economy and sustainable future

Erwin Reisner

Chanon Pornrungroj

Device for making solar fuels on the River Cam near the Bridge of Sighs

̽��ֱ��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.

Yes

Floating ‘artificial leaves’ ride the wave of clean fuel production

sc604 — Wed, 17 Aug 2022 14:58:44 +0000

Researchers have developed floating ‘artificial leaves’ that generate clean fuels from sunlight and water, and could eventually operate on a large scale at sea.

Tiny ‘skyscrapers’ help bacteria convert sunlight into electricity

sc604 — Mon, 07 Mar 2022 16:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, used 3D printing to create grids of high-rise ‘nano-housing’ where sun-loving bacteria can grow quickly. ̽��ֱ��researchers were then able to extract the bacteria’s waste electrons, left over from photosynthesis, which could be used to power small electronics.

Other research teams have extracted energy from photosynthetic bacteria, but the Cambridge researchers have found that providing them with the right kind of home increases the amount of energy they can extract by over an order of magnitude. ̽��ֱ��approach is competitive against traditional methods of renewable bioenergy generation and has already reached solar conversion efficiencies that can outcompete many current methods of biofuel generation.

Their results, reported in the journal Nature Materials, open new avenues in bioenergy generation and suggest that ‘biohybrid’ sources of solar energy could be an important component in the zero-carbon energy mix.

Current renewable technologies, such as silicon-based solar cells and biofuels, are far superior to fossil fuels in terms of carbon emissions, but they also have limitations, such as a reliance on mining, challenges in recycling, and a reliance on farming and land use, which results in biodiversity loss.

“Our approach is a step towards making even more sustainable renewable energy devices for the future,” said Dr Jenny Zhang from the Yusuf Hamied Department of Chemistry, who led the research.

Zhang and her colleagues from the Department of Biochemistry and the Department of Materials Science and Metallurgy are working to rethink bioenergy into something that is sustainable and scalable.

Photosynthetic bacteria, or cyanobacteria, are the most abundant life from on Earth. For several years, researchers have been attempting to ‘re-wire’ the photosynthesis mechanisms of cyanobacteria in order to extract energy from them.

“There’s been a bottleneck in terms of how much energy you can actually extract from photosynthetic systems, but no one understood where the bottleneck was,” said Zhang. “Most scientists assumed that the bottleneck was on the biological side, in the bacteria, but we’ve found that a substantial bottleneck is actually on the material side.”

In order to grow, cyanobacteria need lots of sunlight – like the surface of a lake in summertime. And in order to extract the energy they produce through photosynthesis, the bacteria need to be attached to electrodes.

̽��ֱ��Cambridge team 3D-printed custom electrodes out of metal oxide nanoparticles that are tailored to work with the cyanobacteria as they perform photosynthesis. ̽��ֱ��electrodes were printed as highly branched, densely packed pillar structures, like a tiny city.

Zhang’s team developed a printing technique that allows control over multiple length scales, making the structures highly customisable, which could benefit a wide range of fields.

“ ̽��ֱ��electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” said Zhang. “Cyanobacteria need something they can attach to and form a community with their neighbours. Our electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper.”

Once the self-assembling cyanobacteria were in their new ‘wired’ home, the researchers found that they were more efficient than other current bioenergy technologies, such as biofuels. ̽��ֱ��technique increased the amount of energy extracted by over an order of magnitude over other methods for producing bioenergy from photosynthesis.

“I was surprised we were able to achieve the numbers we did – similar numbers have been predicted for many years, but this is the first time that these numbers have been shown experimentally,” said Zhang. “Cyanobacteria are versatile chemical factories. Our approach allows us to tap into their energy conversion pathway at an early point, which helps us understand how they carry out energy conversion so we can use their natural pathways for renewable fuel or chemical generation.”

̽��ֱ��research was supported in part by the Biotechnology and Biological Sciences Research Council, the Cambridge Trust, the Isaac Newton Trust and the European Research Council. Jenny Zhang is BBSRC David Phillips Fellow in the Department of Chemistry, and a Fellow of Corpus Christi College, Cambridge.

Reference:
Xiaolong Chen et al. ‘3D-printed hierarchical pillar array electrodes for high performance semi-artificial photosynthesis.’ Nature Materials (2022). DOI: 10.1038/s41563-022-01205-5

Researchers have made tiny ‘skyscrapers’ for communities of bacteria, helping them to generate electricity from just sunlight and water.

Our approach is a step towards making even more sustainable renewable energy devices for the future

Jenny Zhang

Gabriella Bocchetti

3D-printed custom electrodes

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 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.

Yes

Women in STEM: Dr Jenny Zhang

sc604 — Thu, 05 Dec 2019 07:00:00 +0000

It was my mother who first got me interested in science. When I was very young, back when I was growing up China, she used to tell me bedtime stories about the origins of thunder and lightning, how radios work, or how eggs became chickens. This apparently had a profound effect on me. Eggs would regularly go missing from the kitchen and turn up buried snugly under some blankets in bed. Or the new radio would be found dismantled, presumably taken apart by someone who wanted a better look inside...

My PhD research was in medicinal chemistry. My aim was to design anti-cancer drugs that could penetrate deep into solid tumours. To achieve this, I synthesised a library of novel DNA intercalators and anti-cancer platinum complexes and studied their bio-distribution and metabolism within 3D-tumour models using a variety of chemical imaging techniques. My research was very much directed by the problem, which gave me opportunities to travel around the world to work in different labs and disciplines. I was able to arrive at new drug design strategies using this approach.

Environmental sustainability is important to me, so that’s why I moved into artificial photosynthesis. My PhD research was highly interdisciplinary and I developed a deep appreciation of how different approaches can breathe fresh ideas into old problems and can often catalyse breakthroughs. Artificial photosynthesis for sustainable fuel development is also a highly interdisciplinary field, and as a research area, it aligns with my personal values about the importance of environmental sustainability.

I came to the Department of Chemistry more than five years ago as a Marie Curie Incoming International Fellow to work on artificial photosynthesis in Professor Erwin Reisner’s group. I was excited by the notion that, coming from quite a different background, I would be able to bring unique perspectives into the field. I also liked the idea of being immersed in a new learning experience. It turned out to be more challenging – and at the same time more fulfilling – than I expected.

We’ve designed new catalytic systems to turn sunlight into 'solar fuels'. In my postdoctoral research, I was interested in turning sunlight into chemical fuels we call 'solar fuels' – sustainable and green alternatives to our current unsustainable and polluting carbon-based fuels. Plants have been carrying out this for millions of years through the process of photosynthesis, enabled by a set of special proteins that make up the photosynthetic electron transport chain. I coordinated a team that studied these enzymes and the reactions that they carry out. We incorporated them into several prototype systems that can use sunlight to turn water into hydrogen. We hope this work will help make such fuels available to everyone in future.

We still need to understand the basic chemistry and physics behind many components of photosynthesis. There are many fundamental questions that remain to be answered both within biological and artificial photosynthetic systems. Mainly, these relate to the flow of electrons and how they can be more efficiently generated and used in catalysis. During my postdoctoral research, I wired photosystem II, nature’s water oxidation enzyme that kick-starts photosynthesis, to custom-made electrodes to study enzyme functionality and to perform light-driven fuel forming reactions. This allowed me to understand the ‘bottlenecks’ of different types of photosynthetic systems, and where improvements need to be made.

My BBSRC Fellowship allows me to drive my own research vision with my own research group. I started my own research group in 2018, and my focus is to develop new tools and approaches for studying photosynthesis (both biological and artificial) and utilising it in renewable energy generation and agricultural/sensor technologies. I’m supported by a generous grant that enables me to have postdocs and the necessary equipment – in particular, a sophisticated 3D printer that can print a large variety of materials, from living cells to metals.

̽��ֱ��Fellowship will also help me build my leadership skills. It aims to get Fellows on the trajectory to leading our own research groups confidently and successfully. We have a BBSRC mentor that comes to visit our lab once a year. I’ve also attended workshops where I learned about the economy of science and leadership. I really like that this scheme offers not just money but the necessary support to help me become a well-rounded leader in science. I feel incredibly lucky to have this opportunity.

I hope my career will lead to the uncovering of many ‘unknown unknowns’. I want to drive innovative and high-value research that addresses important problems in our world today, and I want to achieve this while fostering a healthy and positive lab culture. Like any scientist, I hope my career will lead to the uncovering of many ‘unknown unknowns’ that will leave a positive impact on the world.

It’s important to me that we inspire more students – both girls and boys – to choose science. I still turn up to meetings and workshops where I am either the only woman or one of the few women present. However, this is happening less and less, and I feel that there is a real effort being made by our institutions to be inclusive and to lower barriers. ̽��ֱ��old barriers still exist, but I’m optimistic since I know how determined women can be.

In the meantime, I think we shouldn’t forget about positive action being needed to foster men to challenge their own status quo to become strong counterparts of the future.

Dr Jenny Zhang is a group leader and BBSRC David Phillips Fellow in the Department of Chemistry, where she is re-wiring photosynthesis to generate renewable fuels. Here, she tells us about why she switched from cancer research to sustainability, how her Fellowship programme is helping her develop leadership skills, and why eggs in her childhood home would regularly go missing.

Yes

Scientists pioneer a new way to turn sunlight into fuel

hll43 — Mon, 03 Sep 2018 15:00:00 +0000

Photosynthesis is the process plants use to convert sunlight into energy. Oxygen is produced as a by-product of photosynthesis when the water absorbed by plants is ‘split’. It is one of the most important reactions on the planet because it is the source of nearly all of the world’s oxygen. Hydrogen which is produced when the water is split could potentially be a green and unlimited source of renewable energy.

A new study, led by academics at the ̽��ֱ�� of Cambridge, used semi-artificial photosynthesis to explore new ways to produce and store solar energy. They used natural sunlight to convert water into hydrogen and oxygen using a mixture of biological components and manmade technologies.

̽��ֱ��research could now be used to revolutionise the systems used for renewable energy production. A new paper, published in Nature Energy, outlines how academics at the Reisner Laboratory in Cambridge's Department of Chemistry developed their platform to achieve unassisted solar-driven water-splitting.

Their method also managed to absorb more solar light than natural photosynthesis.

Katarzyna Sokół, first author and PhD student at St John’s College, said: “Natural photosynthesis is not efficient because it has evolved merely to survive so it makes the bare minimum amount of energy needed – around 1-2 per cent of what it could potentially convert and store.”

Artificial photosynthesis has been around for decades but it has not yet been successfully used to create renewable energy because it relies on the use of catalysts, which are often expensive and toxic. This means it can’t yet be used to scale up findings to an industrial level.

̽��ֱ��Cambridge research is part of the emerging field of semi-artificial photosynthesis which aims to overcome the limitations of fully artificial photosynthesis by using enzymes to create the desired reaction.

Sokół and the team of researchers not only improved on the amount of energy produced and stored, they managed to reactivate a process in the algae that has been dormant for millennia.

She explained: “Hydrogenase is an enzyme present in algae that is capable of reducing protons into hydrogen. During evolution, this process has been deactivated because it wasn’t necessary for survival but we successfully managed to bypass the inactivity to achieve the reaction we wanted – splitting water into hydrogen and oxygen.”

Sokół hopes the findings will enable new innovative model systems for solar energy conversion to be developed.

She added: “It’s exciting that we can selectively choose the processes we want, and achieve the reaction we want which is inaccessible in nature. This could be a great platform for developing solar technologies. ̽��ֱ��approach could be used to couple other reactions together to see what can be done, learn from these reactions and then build synthetic, more robust pieces of solar energy technology.”

This model is the first to successfully use hydrogenase and photosystem II to create semi-artificial photosynthesis driven purely by solar power.

Dr Erwin Reisner, Head of the Reisner Laboratory, a Fellow of St John’s College, ̽��ֱ�� of Cambridge, and one of the paper’s authors described the research as a ‘milestone’.

He explained: “This work overcomes many difficult challenges associated with the integration of biological and organic components into inorganic materials for the assembly of semi-artificial devices and opens up a toolbox for developing future systems for solar energy conversion.”

Reference:
Katarzyna P. Sokół et al. 'Bias-free photoelectrochemical water splitting with photosystem II on a dye-sensitized photoanode wired to hydrogenase.' Nature Energy (2018). DOI: 10.1038/s41560-018-0232-y

Originally published on the St John's College website.

̽��ֱ��quest to find new ways to harness solar power has taken a step forward after researchers successfully split water into hydrogen and oxygen by altering the photosynthetic machinery in plants.

This could be a great platform for developing solar technologies.

Katarzyna Sokół

Experimental two-electrode setup showing the photoelectrochemical cell illuminated with simulated solar light

Yes

Non-toxic alternative for next-generation solar cells

sc604 — Tue, 18 Jul 2017 09:00:50 +0000

̽��ֱ��team of researchers, from the ̽��ֱ�� of Cambridge and the United States, have used theoretical and experimental methods to show how bismuth – the so-called “green element” which sits next to lead on the periodic table, could be used in low-cost solar cells. Their results, reported in the journal Advanced Materials, suggest that solar cells incorporating bismuth can replicate the properties that enable the exceptional properties of lead-based solar cells, but without the same toxicity concerns. Later calculations by another research group showed that bismuth-based cells can convert light into energy at efficiencies up to 22%, which is comparable to the most advanced solar cells currently on the market.

Most of the solar cells which we see covering fields and rooftops are made from silicon. Although silicon is highly efficient at converting light into energy, it has a very low “defect tolerance”, meaning that the silicon needs to have very high levels of purity, making it energy-intensive to produce.

Over the past several years, researchers have been looking for materials which can perform at similar or better levels to silicon, but that don’t need such high purity levels, making them cheaper to produce. ̽��ֱ��most promising group of these new materials are called hybrid lead halide perovskites, which appear to promise a revolution in the field of solar energy.

As well as being cheap and easy to produce, perovskite solar cells have, in the space of a few years, become almost as energy-efficient as silicon. However, despite their enormous potential, perovskite solar cells are also somewhat controversial within the scientific community, since lead is integral to their chemical structure. Whether the lead contained within perovskite solar cells represents a tangible risk to humans, animals and the environment is being debated, however, some scientists are now searching for non-toxic materials which could replace the lead in perovskite solar cells without negatively affecting performance.

“We wanted to find out why defects don’t appear to affect the performance of lead-halide perovskite solar cells as much as they would in other materials,” said Dr Robert Hoye of Cambridge’s Cavendish Laboratory and Department of Materials Science & Metallurgy, and the paper’s lead author. “If we can figure out what’s special about them, then perhaps we can replicate their properties using non-toxic materials.”

In collaboration with colleagues at MIT, the National Renewable Energy Laboratory and Colorado School of Mines in the US, the Cambridge researchers have shown that bismuth, which sits next to lead in the periodic table, could be a non-toxic alternative to lead for use in next-generation solar cells. Bismuth, known as the “green element”, is widely used in cosmetics, personal care products and medicines. Like lead, it is a heavy metal, but it is non-toxic.

For this study, Hoye and his colleagues looked at bismuth oxyiodide, a material which was previously investigated for use in solar cells and water splitting, but was not thought to be suitable because of low efficiencies and because it degraded in liquid electrolytes. ̽��ֱ��researchers used theoretical and experimental methods to revisit this material for possible use in solid-state solar cells.

They found that bismuth oxyiodide is as tolerant to defects as lead halide perovskites. Bismuth oxyiodide is also stable in air for at least 197 days, which is a significant improvement over some lead halide perovskite compounds. By sandwiching the bismuth oxyiodide light absorber between two oxide electrodes, they were able to demonstrate a record performance, with the device converting 80% of light to electrical charge.

̽��ֱ��bismuth-based devices can be made using common industrial techniques, suggesting that they can be produced at scale and at low cost.

“Bismuth oxyiodide has all the right physical property attributes for new, highly efficient light absorbers,” said co-author Professor Judith Driscoll, of the Department of Materials Science and Metallurgy. “I first thought of this compound around five years ago, but it took the highly specialised experimental and theoretical skills of a large team for us to prove that this material has real practical potential.”

“This work shows that earlier theories about bismuth oxyiodide were not wrong, and these compounds do have the potential to be successful solar cells,” said Hoye, who is a Junior Research Fellow at Magdalene College. “We’re just scratching the surface of what these compounds can do.”

“Previously, the global solar cell research community has been searching for non-toxic materials that replicate the defect tolerance of the perovskites, but without much success in terms of photovoltaic performance,” said Dr David Scanlon, a theorist at UCL not involved in this work. “When I saw this work, my team calculated based on the optical properties that bismuth oxyiodide has a theoretical limit of 22% efficiency, which is comparable to silicon and the best perovskite solar cells. There’s a lot more we could get from this material by building off this team’s work.”

Reference
Robert Hoye et al. ‘Strongly Enhanced Photovoltaic Performance and Defect Physics of Air-Stable Bismuth Oxyiodide (BiOI).’ Advanced Materials (2017). DOI: 10.1002/adma.201702176

Researchers have demonstrated how a non-toxic alternative to lead could form the basis of next-generation solar cells.

We’re just scratching the surface of what these compounds can do.

Robert Hoye

Steve Penney

Bismuth oxyiodide light absorbers

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