“Artificial leaf” produces fuel and water

Reisner has been working for more than a decade on using the energy of sunlight to produce an energy source, based on the example of plants. While plants use photosynthesis to produce sugar, the researchers wanted to sustainably produce “synthesis gas” using an artificial leaf directly from carbon dioxide (CO2) and water at room temperature. With a first prototype presented in 2019, Reisner and his team from the University of Cambridge (Great Britain) achieved this goal and have since continuously improved and developed the system in different directions.

Their latest achievement simultaneously makes the splitting of water into hydrogen and oxygen possible, thereby enabling the production of green fuel and the purification of polluted water or seawater. Until now, very clean water was required, especially for water splitting, because any contamination would have poisoned the catalyst required for this or would have led to undesirable chemical side reactions.

Even seawater can be used
Together with his PhD students Chanon Pornrungroj and Ariffin Mohamad Annuar, Reisner has now further developed the system so that it also works with contaminated water or seawater. For this they used a nanostructured carbon network that floats on the (dirty) water and keeps the sensitive photocatalyst away from it. This network absorbs visible and infrared light very well, causing it to heat up and produce clean water vapor, which the photocatalyst splits into hydrogen and oxygen with the help of the sun’s UV light.

This arrangement allows more solar energy to be used: the catalyst uses only a small part of the spectrum of sunlight (UV light) to produce hydrogen. The remaining light reaches the bottom of the system, where it heats the carbon network, causing the water to evaporate. Some of the water vapor can then be used to produce hydrogen, but some can also be collected as clean water and used for other purposes. “In this way we really imitate a real leaf, because we can now involve the process of transpiration,” Reisner explains.

Tests of the system showed that it can produce clean water and then hydrogen even from polluted water and seawater. “We were even able to test this successfully in the River Cam in central Cambridge,” says the chemist, who puts hydrogen production efficiency at 0.14 percent and water vapor production at 0.95 kilograms per square meter per hour.

Clean fuel and clean drinking water
Such a system, which also works with heavily polluted water, could be especially interesting for remote areas with few resources, as it can produce both clean fuel and clean drinking water without an external energy source. The researchers point not only to the billions of people who do not have access to clean drinking water, but also to the millions of deaths per year that, according to the World Health Organization (WHO), are caused by cooking with ‘dirty’ fuels such as kerosene. indoors.

“There is still a lot to do, but we have been able to provide basic evidence that the art magazine works,” Reisner emphasizes. Climate crisis, pollution and health are closely linked. “Developing an approach that could help solve both problems would be critical for so many people.”

British Prime Minister Rishi Sunak obviously sees it that way too. In a recent speech on achieving his country’s climate goals, he presented the technology developed by Cambridge researchers to produce fuel using sunlight as one of the most promising innovations to achieve climate goals. . In addition, Reisner’s group recently received the Royal Society’s Hughes Medal for this work, and the International Union for Pure and Applied Chemistry (IUPAC) last year ranked the technology as one of the top ten emerging technologies in chemistry.