Solar-powered leaf points the way to a decarbonized chemical industry
Researchers from the University of Cambridge have built a solar-powered biohybrid that converts sunlight, water and carbon dioxide into formate, a fuel and versatile building block for downstream synthesis. The team says such devices could help de-fossilize the chemical production responsible for about 6% of global carbon emissions.
Their semi-artificial leaf couples light-harvesting organic polymers to bacterial enzymes, mimicking photosynthesis without external force. Unlike previous prototypes that used toxic or unstable absorbers, the new design omits dangerous semiconductors, improves durability and operates without additional chemicals that previously limited efficiency.
In proof-of-concept tests, the leaf produced formate using sunlight and then fed it directly into a domino reaction to yield a pharmaceutically relevant compound in high purity and yield. The study, published in Joule, is the first to use organic semiconductors as a light-collecting element in this class of biohybrid devices.
“If we want to build a circular, sustainable economy, the chemical industry is a big, complex problem that we need to tackle,” said Professor Erwin Reisner from the Yusuf Hamied Department of Chemistry in Cambridge, who led the research. “We need to think of ways to defossilize this important sector that produces so many important products we all need. It’s a huge opportunity if we can get it right.”
Reisner’s group has long developed artificial leaves that convert sunlight into carbon-based fuels and chemicals. Many previous systems relied on inorganic semiconductors or synthetic catalysts that broke down quickly, wasted parts of the solar spectrum or contained toxic elements such as lead.
“If we can remove the toxic components and start using organic elements, we get a clean chemical reaction and a single end product, without unwanted side reactions,” says co-first author Dr. Celine Yeung, who completed the research as part of her PhD work in Reisner’s laboratory. “This device combines the best of both worlds: organic semiconductors are tunable and non-toxic, while biocatalysts are highly selective and efficient.”
The device integrates organic semiconductors with enzymes from sulfate-reducing bacteria to split water into hydrogen and oxygen or to reduce carbon dioxide to formate. By embedding carbonic anhydrase in a porous titanium matrix, the team enabled operation in a simple bicarbonate solution, similar to carbonated water, eliminating the need for unstable buffer additives.
“It’s like a big puzzle,” says co-first author Dr. Yongpeng Liu, a postdoctoral researcher in Reisner’s lab. “We have all these different components that we’ve been trying to bring together for a single purpose. It took us a long time to figure out how this specific enzyme gets immobilized on an electrode, but we are now starting to see the fruits of these efforts.”
“By really studying how the enzyme works, we were able to precisely design the materials that make up the different layers of our sandwich-like device,” says Yeung. “This design allowed the parts to work together more effectively, from the tiny nanoscale to the full artificial leaf.”
Performance tests showed high photocurrents and near-perfect electron utilization for fuel-forming reactions. The art tray worked continuously for more than 24 hours, more than twice as long as previous designs. Next steps include extending its lifespan and adapting the platform to create additional target chemicals.
“We have shown that it is possible to create solar-powered devices that are not only efficient and durable, but also free of toxic or unsustainable components,” said Reisner. “This could be a fundamental platform for the production of green fuels and chemicals in the future – it is a real opportunity to do exciting and important chemistry.”
The research received support from A*STAR Singapore, the European Research Council, the Swiss National Science Foundation, the Royal Academy of Engineering and UKRI. Reisner is a Fellow of St John’s College, Cambridge; Yeung is a fellow of Downing College, Cambridge.
Research report:Semi-artificial leaf interfaces with organic semiconductors and enzymes for chemical synthesis of solar energy
