LMU Professor Emiliano Cortes is revolutionizing the capture of solar energy through nanotechnology. By developing plasmonic nanostructures, his team is creating materials that focus solar energy more efficiently. Their latest advance is a supercrystal that uses sunlight to produce hydrogen from formic acid, and they hold a world record in this field. Credit: SciTechDaily.com
Hydrogen is a building block of the energy transition. To obtain it with the help of solar energy, LMU researchers have developed new high-performance nanostructures. This material holds the world record for solar-powered green hydrogen production.
When Emiliano Cortés goes out in search of sunlight, he doesn’t use giant mirrors or vast solar farms. On the contrary, LMU’s Professor of Experimental Physics and Energy Conversion dives into the nanocosmos. “Our research begins when photons, the energetic particles of sunlight, encounter atomic structures,” Cortes said. “We are working on material solutions to capture and use solar energy more efficiently.”
Innovative solutions for solar energy
His discoveries have great potential to enable new solar cells and photocatalysts. The industry has high hopes for the latter, as it can bypass the need for electricity generation and allow light energy to be used in chemical reactions. But Cortez knows there’s one big challenge to harnessing sunlight, and solar cells have to deal with it, too. “Sunlight reaches the earth ‘diluted’, so it has relatively low energy per area.” Solar panels compensate for this by covering a large area.
Emiliano Cortes works on material solutions to capture and use solar energy more efficiently. Credit: © Nano Energy Group
But Cortes approaches the problem from a different direction, so to speak. His team at LMU’s Nano Institute is particularly funded by the Cluster of Excellence in Electron Conversion and the Hybridization of Solar Technologies (Initiative). He is developing his so-called plasmonic nanostructures, which can be used to focus solar energy, at the Bavarian State Museum and the European Research Council.
A breakthrough in solar energy conversion
In recent publications in magazines natural catalysisDr. Cortés, together with Dr. Matthias Hellan, currently at the Fritz Haber Institute in Berlin, and collaborative partners from the Free University of Berlin and the University of Hamburg, presented a two-dimensional supercrystal for producing hydrogen from formic acid. acid With the help of sunlight.
“In fact, this material is so good that it holds the world record for hydrogen production using sunlight,” Cortes points out. This is good news for the production of both photocatalysts and hydrogen as an energy carrier. Because they play a key role in the success of the energy transition.
Focusing solar energy using small magnets
Cortes and Herran use two different metals for their supercrystals. nanoscale format. “First, from a plasmonic metal (gold in our case) he creates particles in the range of 10 to 200 nanometers,” Herran explains. “At this scale, a special phenomenon occurs in plasmonic metals such as silver, copper, aluminum, and magnesium. Visible light interacts very strongly with the metal’s electrons, causing resonant vibrations in the metal.”
This means that the electrons collectively move very quickly from one side of the nanoparticle to the other, forming a kind of mini-magnet. Experts call this the dipole moment. “For the incident light, this is a strong change, so it then interacts more strongly with the metal nanoparticles,” Cortes explains. “Likewise, you can think of this process as a superlens that focuses energy. Our nanomaterials do that on a molecular scale.” This allows the nanoparticles to capture more sunlight and It can be converted into very high energy electrons. These further help to accelerate chemical reactions.
Nanohotspots unleash catalytic power
But how can this energy be harnessed? To this end, LMU scientists collaborated with researchers from the University of Hamburg. They arranged the gold particles regularly on the surface, following the principle of self-assembly. To maximize the interaction of light and matter, the particles must be very close together, but not in contact.
LMU researchers, in collaboration with a research team from the Freie Universität Berlin who studied the optical properties of the material, found that the absorption of light increases many times. “Gold nanoparticle arrays focus incoming light very efficiently, creating highly localized strong electric fields, so-called hot spots,” Herran says.
These form between gold particles, which gave Cortés and Herran the idea to place nanoparticles of platinum, a classical and powerful catalytic material, in the gaps. This was also done by a research team in Hamburg.
“Platinum is not a suitable material for photocatalysis because it does not absorb much sunlight. However, we can force the absorption at hot spots and enhance the chemical reactions caused by light energy. In our case. , the reaction converts formic acid to hydrogen,” Herran explains.
With a hydrogen production rate of 139 mmol per gram of catalyst per hour from formic acid, this photocatalytic material currently holds the world record for hydrogen production.2 Production using sunlight.
Towards sustainable hydrogen production
Currently, hydrogen is mainly produced from fossil fuels, primarily natural gas. To switch to more sustainable production, research teams around the world are working on technologies that use alternative raw materials such as formic acid, ammonia and water. A focus is also placed on the development of photocatalytic reactors suitable for large-scale production. “Smart materials solutions like ours are a critical component for the success of the technology,” he said of the two researchers.
“By combining plasmonic and catalytic metals, we are developing powerful photocatalysts for industrial applications. This is a new way to use sunlight and has the potential for other reactions, such as the conversion of CO. brings.2 Convert it into a usable substance,” Cortes and Herran explain. The two researchers have already obtained a patent for their material development.
Reference: “Plasmonic bimetallic two-dimensional supercrystals for H2 production” Matias Herran, Sabrina Juergensen, Moritz Kessens, Dominik Hoeing, Andrea Köppen, Ana Sousa-Castillo, Wolfgang J. Parak, Holger Lange, Stephanie Reich, Florian Schulz , by Emiliano Cortés, November 30, 2023, natural catalysis.
DOI: 10.1038/s41929-023-01053-9
