In the endless pursuit of renewable, clean energy, scientists from the University of Cambridge claim to have built a standalone device that can mimic photosynthesis and convert sunlight, carbon dioxide, and water into liquid fuel.

The study, published in Nature Energy, outlines a new method that allows the production of clean fuel from the most basic inputs, all whilst being completely wireless. Requiring no electrical input, the researchers believe this carbon-neutral method of energy generation could be scaled up to produce large amounts of fuel in a sustainable way, and could be used to produce massive solar farms comprised of cells performing artificial photosynthesis.

By utilizing "photosheet" technology, which is a sheet containing photocatalysts, the device is able to use sunlight to convert CO₂ and water into oxygen and formic acid. The formic acid can be stored as a liquid, or converted relatively simply into hydrogen, which has a variety of applications from industrial processes to space travel.

Previous attempts of creating artificial photosynthesis devices have suffered from producing a huge amount of waste product and therefore are too inefficient to be useful on a grand scale, but the team believes this breakthrough device is the most hopeful yet.

“It’s been difficult to achieve artificial photosynthesis with a high degree of selectivity, so that you’re converting as much of the sunlight as possible into the fuel you want, rather than be left with a lot of waste,” said first author Dr Qian Wang, a Marie Curie Fellow and a postdoctoral researcher in the Reisner Lab, in a statement.

“In addition, storage of gaseous fuels and separation of by-products can be complicated — we want to get to the point where we can cleanly produce a liquid fuel that can also be easily stored and transported,” said Professor Erwin Reisner, the paper’s senior author.

The technology produces clean fuel that can be stored safely and easily, whilst maintaining the ability to be scaled up to the sizes needed for industrial needs. Whilst the current device is just 20 cm², the team believe larger cells would be easy to create.

Reisner and colleagues from Cambridge produced a similar technology back in 2019, in which an "artificial leaf" would convert the same ingredients of CO₂, water, and sunlight into fuel, but the fuel created was a synthetic gas (called syngas), which is significantly harder to store. The products of this device are much more stable, and the process is far more robust, giving the researchers hope the technology can be more widely applicable. 

Whilst the technology is promising, it isn’t ready for the mass market quite yet. The catalyst used on the photosheet is based on cobalt, which sadly isn’t efficient enough for it to be a viable method of fuel production on a large scale. The team will continue pursuing different options and improving the device, so photosynthesis-powered energy production could be closer than you think.