This artificial leaf turns pollution into power

Now, a team led by the University of Cambridge is exploring innovative approaches that could eventually “de-fossilize” this vital industry.

Their breakthrough involves a hybrid device that brings together light-absorbing organic polymers and bacterial enzymes to transform sunlight, water, and carbon dioxide into formate, a clean fuel that can power additional chemical reactions.

This “semi-artificial leaf” replicates photosynthesis, the natural process plants use to turn sunlight into energy, and operates entirely on its own power. Unlike previous designs that relied on toxic or unstable light absorbers, this new biohybrid model uses non-toxic materials, runs more efficiently, and remains stable without extra additives.

In laboratory tests, the team successfully used sunlight to convert carbon dioxide into formate and then applied it directly in a “domino” reaction to synthesize a valuable compound used in pharmaceuticals, achieving both high yield and purity.

According to findings published in Joule, this marks the first instance where organic semiconductors have served as the light-capturing component in such a biohybrid system, paving the way for a new generation of eco-friendly artificial leaves.

The chemical industry remains a cornerstone of the global economy, producing a vast range of goods—from medicines and fertilizers to plastics, paints, electronics, cleaning agents, and toiletries.

“If we’re going to build a circular, sustainable economy, the chemical industry is a big, complex problem that we must address,” said Professor Erwin Reisner from Cambridge’s Yusuf Hamied Department of Chemistry, who led the research. “We’ve got to come up with ways to de-fossilize this important sector, which produces so many important products we all need. It’s a huge opportunity if we can get it right.”

Reisner’s research group specializes in the development of artificial leaves, which turn sunlight into carbon-based fuels and chemicals without relying on fossil fuels. But many of their earlier designs depend on synthetic catalysts or inorganic semiconductors, which either degrade quickly, waste much of the solar spectrum, or contain toxic elements such as lead.

“If we can remove the toxic components and start using organic elements, we end up with a clean chemical reaction and a single end product, without any unwanted side reactions,” said co-first author Dr. Celine Yeung, who completed the research as part of her PhD work in Reisner’s lab. “This device combines the best of both worlds – organic semiconductors are tuneable and non-toxic, while biocatalysts are highly selective and efficient.”

The new device integrates organic semiconductors with enzymes from sulfate-reducing bacteria, splitting water into hydrogen and oxygen or converting carbon dioxide into formate.

The researchers have also addressed a long-standing challenge: most systems require chemical additives, known as buffers, to keep the enzymes running. These can break down quickly and limit stability. By embedding a helper enzyme, carbonic anhydrase, into a porous titania structure, the researchers enabled the system to work in a simple bicarbonate solution — similar to sparkling water — without unsustainable additives.

“It’s like a big puzzle,” said 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 is immobilized on an electrode, but we’re now starting to see the fruits from 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,” said Yeung. “This design made the parts work together more effectively, from the tiny nanoscale up to the full artificial leaf.”

Tests showed the artificial leaf produced high currents and achieved near-perfect efficiency in directing electrons into fuel-making reactions. The device successfully ran for over 24 hours: more than twice as long as previous designs.

The researchers are hoping to further develop their designs to extend the lifespan of the device and adapt it so it can produce different types of chemical products.

“We’ve shown it’s possible to create solar-powered devices that are not only efficient and durable but also free from toxic or unsustainable components,” said Reisner. “This could be a fundamental platform for producing green fuels and chemicals in future – it’s a real opportunity to do some exciting and important chemistry.”

The research was supported in part by the Singapore Agency for Science, Technology and Research (A*STAR), the European Research Council, the Swiss National Science Foundation, the Royal Academy of Engineering, and UK Research and Innovation (UKRI). Erwin Reisner is a Fellow of St John’s College, Cambridge. Celine Yeung is a Member of Downing College, Cambridge.