Foglia artificiale

The artificial leaf

A device that replicates photosynthesis to convert CO₂, sunlight and water into energy and oxygen.

by Maria Pia Rossignaud
30 November 2020
5 min read
by Maria Pia Rossignaud
30 November 2020
5 min read

Renaissance thinkers pondered the importance of imitating nature because therein lay the beauty of the world. What if their theories could save the climate now? Imagine an artificial piece of equipment that could reproduce the process of photosynthesis, so that we could get rid of greenhouse gases and absorb light and water to make energy. Scientists all over the world have been trying for years, and success has never been so near our grasp.

Photosynthesis at hand

A study that appeared in the magazine Nature Energy shows how a team of British researchers from the Department of Chemistry at Cambridge, in collaboration with a group from Tokyo University, managed in their laboratory to create a prototype artificial leaf, a device that converts carbon dioxide and water into oxygen and formic acid. This derivative can be used directly as a fuel, stored or used in hydrogen production to activate other production processes. The potentially revolutionary scope of this technology is clear to see. Not only would it use a totally clean energy source –the Sun– it would also limit the effects of CO2 emissions and make the atmosphere cleaner.

According to Qian Wang, the first signatory of the article, the trickiest part was getting "a high degree of selectivity" in the way the artificial leaf works, “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”. In the statements accompanying the research as it was published on the university’s official website, Qian Wang adds, "We were surprised how well it worked in terms of its selectivity – it produced almost no by-products”.

A new version

As is often the case in scientific research, the discovery didn’t come from nowhere. The Anglo-Japanese research team succeeded in perfecting an earlier version of the artificial leaf, developed in 2019 by a group led by Professor Erwin Reisner of the same university. The prototype used little solar cells to absorb the light, water and carbon dioxide it needed to produce syngas – specifically carbon monoxide and hydrogen, two intermediates used in the chemicals industry and in energy production.

In its new incarnation, the device takes the form of a leaf and the technology it’s based on uses a cobalt photocatalyst fed with semi-conductive powders, which activate redox reactions when sunlight hits its surface in the presence of water. These leaves can be made in large quantities quite simply and cheaply. This new kind of artificial photosynthesis also rests on firmer ground than its predecessor. It produces formic acid, a fuel that’s easier to store than syngas, and it leaves much room for hope in terms of large-scale fuel production.

The technology now at our disposal can’t be called definitive, but the outlook is more than promising. Researchers are working now to further improve the system and the efficiency of its absorption and yield. The current test piece is 20 cm2 and it should be pretty simple to make new prototypes measuring many square metres. This feature, along with its leaf-like structure, would make it easy to assemble and adapt the device to requirements, suiting it to mass production at relatively low costs. In the same vein, scientists have decided to design the leaves in order that each one is independent and doesn’t need linking up with a cable.

Last touches

But before embarking on commercial production, we need to improve output stability and resolve the problem of storing gaseous fuels and separating byproducts –and that’s a front we haven’t made much progress on yet. On Cambridge’s website you’ll find out that Professor Reisner, who designed the first device and oversaw the latest research, has made their next goal to cleanly produce a liquid fuel that can easily be stored and transported. He concludes: "We hope this technology will pave the way toward sustainable and practical solar fuel production."

The author: Maria Pia Rossignaud

Journalist and expert on digital media writing,  she is one of the twenty-five digital experts of the European Commission Representation in Italy, director of the first Italian digital culture magazine "Media Duemila" and Vice President of the TuttiMedia Observatory.