How the first step affects the (watery) result
German Scientists from Jena and Erlangen-Nürnberg show the way to a more effective creation of hydrogen
In their tests for a more efficient energy conversion the scientists focus on chemical photo catalysts. With this light is being used to let electrons “jump“ well-directed from one subunit of the molecule to the other or to transport them over a ligand, which is a “bridge“.
Like the photosynthesis this process, which the chemists run in the laboratory, works in two main steps: A special metal complex with Ruthenium as its main component serves as an antenna which harvests the light. The Ruthenium then transfers an electron onto the reaction centre. The core of the reaction centre is a Palladium atom. At this metal centre the hydrogen is finally generated. But other than in nature not all electrons reach the palladium centre from the Ruthenium in the laboratory construction. Some choose “detours“, some enter “roundabouts“ or “blind alleys“ and thus are being lost for the reaction. “Supported by resonance Raman spectroscopy we were able to watch and see where the electron ends after directly after the photoexitation,“ describes Prof Dr Juergen Popp, director of IPC and IPHT. „Thereby we were able to develop a new synthesis paradigm“, Michael Schmitt adds. The team of scientists could prove that the efficiency of hydrogen generation depends on the light wavelength. It is more efficient the redder the light used for photo excitation is – light of a wavelength of 550 nm is ideal. “The redder the light the more electrons are transferred to the ligand, that connects the Ruthenium with the Palladium“, Schmitt says. Moreover the initial absorption step decides where the electron goes and thus how effective the generation of energy is.
“This knowledge enables us to put up well-directed barriers so that the electrons don´t take a ,wrong turn’ but exclusively end up at the Palladium“, says Prof Popp explaining the application potential of this fundamental research. In the laboratory the hydrogen generation is four times above former data but still far below the necessary rate. Now it is up to the chemists, like the participating Prof. Dr Sven Rau, to optimize the molecular catalysts, that “no electrons will be taken on by terminal ligands,“ as Schmitt explains.
The scientists know that it is still a long way to go to copy the photosynthesis of nature correctly and efficiently. “But due to our spectroscopic analysis we took a huge step on this way“, Prof Popp is sure though.
Original Publication: Stefanie Tschierlei, Michael Karnahl, Martin Presselt, Benjamin Dietzek, Julien Guthmuller, Leticia González, Michael Schmitt, Sven Rau und Jürgen Popp; „Photochemical Fate: The First Step Determines Efficiency of H2 Formation with a Supramolecular Photocatalyst“, Angew. Chem. Int. Ed. 2010, 122, 3981-3984
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Topic World Spectroscopy
Investigation with spectroscopy gives us unique insights into the composition and structure of materials. From UV-Vis spectroscopy to infrared and Raman spectroscopy to fluorescence and atomic absorption spectroscopy, spectroscopy offers us a wide range of analytical techniques to precisely characterize substances. Immerse yourself in the fascinating world of spectroscopy!
Topic World Spectroscopy
Investigation with spectroscopy gives us unique insights into the composition and structure of materials. From UV-Vis spectroscopy to infrared and Raman spectroscopy to fluorescence and atomic absorption spectroscopy, spectroscopy offers us a wide range of analytical techniques to precisely characterize substances. Immerse yourself in the fascinating world of spectroscopy!