(Jena) – A team from the “CataLight” special research center at the universities of Jena and Ulm has combined novel organic dyes with precious metal-free catalyst molecules. These release gaseous hydrogen in water when exposed to light. A now published study states that the substitute “showed a remarkable impact in terms of longevity and effectiveness after stimulation by visible light.”
Photosynthesis as inspiration
The researchers from the Friedrich Schiller University, the Leibniz Institute for Photonic Technologies (Leibniz-IPHT) and the University of Ulm say they were inspired by nature: “That is where the most effective storage of sunlight takes place in chemical bonds in photosynthesis. In the chloroplasts, “the light collection and reaction complexes are firmly arranged in the thylakoid membrane,” according to the scientists. The researchers in Felix Schacher's working group achieved such an arrangement using polymers that interact with both hydrophilic and hydrophobic substances, according to a statement. These charged graft copolymers are manufactured artificially.
Organic dyes
While most approaches to artificial photosynthesis rely on precious metal complexes as light-absorbing materials, Kalina Peneva's research group is working on metal-free dyes. The people of Jena used Rylene dyes, which are particularly stable to light and chemical processes.
“The light-absorbing metal complexes used in research often contain ruthenium or iridium. “However, these metals make up less than 0,1 millionth of a percent of the mass of the earth’s crust,” says Kalina Peneva, and their use is therefore limited. The use of photoactive compounds based on organic chemicals is “significantly more sustainable than the use of heavy metals”.
Adjust energy level
However, the absorption of light alone does not produce hydrogen. For this to happen, “the energy levels of the dyes and catalyst molecules would have to match each other precisely after absorption.” To determine these energy levels, the researchers in Benjamin Dietzek's working group used spectroscopic methods, in which conclusions about, among other things, the energy absorbed and remaining in the molecule could be drawn from the interaction of matter with defined light.
deep link
https://www.uni-jena.de/201222_Catalight
Publication
D. Costabel, A. Skabeev, A. Nabiyan, Y. Luo, J. Max, A. Rajagopal, D. Kowalczyk, B. Dietzek, M. Wächtler, H. Görls, D. Ziegenbalg, Y. Zagranyarski, C. Streb, FH Schacher, K. Peneva: 1,7,9,10‐tetrasubstituted PMIs accessible via decarboxylative bromination: Synthesis, Characterization, Photophysical Studies and Hydrogen Evolution Catalysis. Chemistry - A European Journal (2020). DOI: 10.1002/chem.202004326
https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202004326
Photos
Researchers at the universities of Jena and Ulm produce hydrogen using novel dyes, precious metal-free catalyst molecules and light. © Anne Günther/University of Jena
