A prototype developed in Tarragona is the latest in a series of devices that seek to convert light into hydrogen
The leaves they use sunlight to transform water and CO2 in the air into oxygen and sugars essential for plants. A century ago, science conceived the idea of emulating them, but it has not been until the last decade when the prototypes that achieve it have multiplied.
The latest in the series is a device developed by the consortium A-LEAF, coordinated from Tarragona. This artificial leaf converts light into hydrogen, a clean fuel when generated from renewable energy. The system has record efficiency in its field and also, contrary to previous prototypes, does not use rare materialswhich would increase its cost and limit its industrial development.
“For a long time, we have focused on small prototypes, but now people are pushing towards scalable and application-compatible systems,” says the artificial leaf expert Virgil Andrey, from Cambridge University, not involved in A-LEAF.
However, the general opinion is that the industrial use of these systems is not close. This implies that their contribution to the achievement of clean fuels would probably reach a significant level after 2050the term established in international agreements to obtain the climate neutrality.
fuel from light
The beauty of artificial leaves is that they allow you to remove clean fuels from the light of the sun. They also put a use to CO2, mainly responsible for global warming.
Currently, light can already be converted into electrical energy by means of solar panels. So why generate fuel? “If you can directly use electrical power, you should. in conversion [a combustible] a lot of energy is lost & rdquor ;, he says Roel van de Krolexpert from the Helmoltz center in Berlin, not involved in A-LEAF.
However, “if you want to store energy for a long time or provide it quickly in very intensive industries, you need fuels,” he explains. José Ramón Galán-Mascarósresearcher at the Institut Català d’Investigació Química (ICIQ), coordinator of A-LEAF.
For example, the clean fuels are the only hope for decarbonize the metallurgical industry, aviation or maritime transport. In these cases, storing electricity in batteries would not work. “Fuels have much more energy density. In one liter there is the same energy as in 50 kilos of batteries,” says Andrei.
Variety of strategies
The easiest way to get green hydrogen is to take energy from solar panels (or another renewable source) and put it in a electrolyser, which produces it from water. “This indirect technique will be the most viable in the coming decades,” observes Van de Krol.
However, coupling these two technologies entails a lot of loss of efficiency and the use of expensive materials. “Artificial leaves try to integrate both concepts from the beginning& rdquor ;, explains Galán.
These try to transform, within a single device, solar energy into chemical energy – that is, store that energy in the chemical bonds of a substance. Specifically, they take light and other materials (such as water, CO2, or nitrogen) and convert them into a variety of products (such as hydrogen).
The artificial leaf of Tarragona
A-LEAF’s artificial leaf uses light and a supply of water and CO2 and produces hydrogen and formic acid. This substance acts as a store, as it contains hydrogen that can be extracted successively. The unique thing about the system is that it uses abundant materials on Earth (such as copper, sulfur, nickel, and iron) as opposed to the expensive and rare ones used in earlier prototypes (such as platinum, indium, and gallium).
The system reaches a high efficiency. 10% of the solar energy it receives is transformed into chemical bonds. As little as it may seem, it is beginning to approach the range of 20% of commercial solar panels, highlights Galán.
The artificial leaf of Tarragona has 5 cm2 of surface and has produced 10 milligrams of green hydrogen and 425 of formic acid in 10 hours of operation. If it were scaled to a surface area of one square meter, it would generate enough energy to charge a mobile forty times in the same time, Galán estimates.
concrete perspectives
“We have shown that it can be achieved with materials and processes cheap& rdquor ;, says the researcher. The independent sources consulted agree on this. “It is a great advance that shows that CO2 can be fixed with high efficiency with a device that does not use prohibitive materials,” he says. erwin reisnerexpert from the University of Cambridge.
However, the road to the industry is long. In addition to increasing the size and efficiency of artificial leaves, it is necessary to make them work stably for a long time under the variable light and temperature conditions of the real world, Andrei points out.
Furthermore, for the moment CO2 It is not known how to systematically remove the food that feeds them from the air and it would have to be found in specific sources, such as the chimney of an industry. “We probably won’t see many artificial leaves around us until 2050,” says van de Krol.