Standalone device creates clean fuels from sunlight, CO2 and water

25 Aug 2020

The standalone device that could one day mass-produce storable, sustainable carbon-neutral fuels. Image: University of Cambridge

Researchers have developed a standalone, wireless device that can convert sunlight, carbon dioxide and water into a carbon-neutral fuel.

Researchers from the University of Cambridge and the University of Tokyo believe they have taken a major step towards achieving large-scale artificial photosynthesis with a new standalone device. Publishing findings to Nature Energy, the team said the device can convert sunlight, CO2 and water into oxygen and formic acid – a storable fuel that can be used by itself or converted into hydrogen fuel.

The wireless device could potentially be scaled up to create ‘energy farms’, similar to solar farms, producing clean fuels to transition industry and transport away from fossil fuels.

Hydrogen is one fuel type that is seen as having significant potential for long-distance or heavy-duty vehicles, with the EU recently announcing plans to produce 10m tonnes of renewable-sourced hydrogen as part of its grand vision of being carbon neutral by 2050.

The research team said that while the idea of harvesting solar energy to convert CO2 into fuel is not new, it is a significant challenge to do it without creating unwanted byproducts.

“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 from Cambridge’s chemistry department.

A rare case

Research in 2019 from the university resulted in an ‘artificial leaf’ that uses sunlight, CO2 and water to create a fuel known as syngas. The new technology looks and behaves similarly to the artificial leaf, but works in a different way and produces formic acid. While the artificial leaf used components from solar cells to harvest sunlight, the new device relies solely on photocatalysts embedded on a sheet to produce a so-called photocatalyst sheet.

The sheets are made up of semiconductor powders, which can be prepared in large quantities easily and cost-effectively. The test device used in experiments was just 20 sq cm in size, but the researchers said it should be relatively straightforward to scale it up to several square metres.

However, the device needs to be made more efficient before it can be considered in any commercial deployment. This means experimenting with a range of different catalysts to improve both stability and efficiency.

“We were surprised how well it worked in terms of its selectivity – it produced almost no by-products,” Wang said. “Sometimes things don’t work as well as you expected, but this was a rare case where it actually worked better.”

Colm Gorey was a senior journalist with Silicon Republic