Team from the University of Cambridge developed a standalone device that converts sunlight, carbon dioxide and water into a carbon-neutral fuel, without requiring any additional components or electricity.
In a report published in Nature Energy, the researchers outlined a new method for converting carbon dioxide into clean fuel through a wireless device. This device could potentially be scaled up for use in energy “farms” similar to solar farms. This presents a significant step forward in achieving artificial photosynthesis. Leveraging on advanced “photosheet” technology, it converts sunlight, carbon dioxide and water into oxygen and formic acid -- a storable fuel that can be either be used directly or be converted into hydrogen.
Harvesting solar energy to convert carbon dioxide into fuel is a promising way to reduce carbon emissions and transition away from fossil fuels. However, it is challenging to produce these clean fuels without unwanted by-products.
“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 Wang Qian from Cambridge's Department of Chemistry.
“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.
A previous development in 2019, the research group created a solar reactor based on an “artificial leaf” design able to use sunlight, carbon dioxide and water to produce fuel, known as syngas. The present novel technology functions similarly to this previous design but processes are different and still produces formic acid.
While the artificial leaf used components from solar cells, the new device doesn't require these components and 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 new technology is more robust and produces clean fuel that is easier to store, enhancing the potential for producing fuel products at larger scale. Additionally, formic acid can be accumulated in solution, and is able to be chemically converted into different types of fuel.
The carbon-dioxide converting cobalt-based catalyst is easy to make and relatively stable. While this technology will be easier to scale up than the artificial leaf, the efficiencies still need to be improved before any commercial deployment can be considered. The researchers are experimenting with a range of different catalysts to improve both stability and efficiency.
The current results were obtained in collaboration with the team of Professor Kazunari Domen from the University of Tokyo, a co-author of the study. The researchers are now working to further optimise the system and improve efficiency. Additionally, they are exploring other catalysts for using on the device to get different solar fuels.