Hydrogen is considered to be the energy carrier of the future – provided it is produced “green”, ie with electricity from renewable energy sources. Researchers in Vienna have now developed a simple method to split water into oxygen and hydrogen using light.
To do this, they combined two catalysts made of relatively inexpensive materials on an atomic-scale semiconductor, they report in the journal “ACS Catalysis” of the American Chemical Society (ACS).
Photocatalytic Water Splitting
In the presence of a suitable catalyst, sunlight can split water (H2O) into oxygen (O2) and hydrogen (H2). This so-called photocatalytic water splitting was discovered exactly 50 years ago in 1972 by the Japanese researchers Akira Fujishima and Kenichi Honda. They showed that titanium dioxide can be used as a catalyst to split H2O into H2 and O2 when exposed to sunlight.
Although this process has since been researched all over the world, its efficiency has not yet increased to the extent that it can be used to efficiently produce hydrogen on an industrial scale. One of the reasons for this is that neither the process course nor the mechanism of action of the catalyst are sufficiently known to allow targeted optimization of the catalyst in the direction of greater efficiency.
Researchers faced two tasks at once
Photocatalytic water splitting involves “two tasks at once,” explains Alexey Cherevan (see video above) of the Institute for Materials Chemistry at the Technical University of Vienna (TU). On the one hand, the oxygen atoms in the water would have to be converted into O2 molecules, and on the other hand, the remaining hydrogen ions would coalesce into H2 molecules.
To achieve this, the Viennese researchers anchor tiny inorganic clusters, consisting of only a small number of atoms, on a light-absorbing substructure such as titanium oxide. The clusters for the production of the oxygen molecules consist of cobalt, tungsten and oxygen, those for the production of hydrogen molecules of sulfur and molybdenum.
“The energy of the absorbed light causes free-moving electrons and free-moving positive charges to be created in the titanium oxide. These charges then make the clusters of atoms sitting on that surface facilitate the splitting of water into hydrogen and oxygen,” Cherevan says.
New method to improve understanding
According to them, the advantage of the method developed by the TU scientists is that they can determine the exact structure of the clusters with atomic precision and thus gain complete insight into the catalytic cycle. The nanoparticles used by other research groups, on the other hand, can take on very different shapes and surface properties. In addition, the size of the particles is difficult to control and their atoms are not always arranged in the same way. This cannot explain the catalytic process in detail.
“We don’t want to just rely on trial and error and trying different nanoparticles until we find the best method — we want to clarify at the atomic level what the optimal catalyst is,” Cherevan explains. Now that it has been proven that the selected materials are indeed suitable for splitting water, the researchers want to further improve the precise structure of the clusters to increase efficiency.
Source: Krone
I’m Wayne Wickman, a professional journalist and author for Today Times Live. My specialty is covering global news and current events, offering readers a unique perspective on the world’s most pressing issues. I’m passionate about storytelling and helping people stay informed on the goings-on of our planet.
