From Sunlight to Hydrogen

• Research team from Jena and Ulm produces hydrogen with the help of light

The production of molecular hydrogen as an alternative, renewable and clean energy source based on water and light is a central element of solar energy conversion and storage. 

A team from the “CataLight” Collaborative Research Center at the Universities of Jena and Ulm has combined novel organic dyes with precious metal-free catalyst molecules that release gaseous hydrogen when exposed to light in water. The study just published states that the substitute has shown a remarkable impact in terms of longevity and effectiveness after stimulation by visible light.

Photosynthesis as inspiration

The researchers at the Friedrich Schiller University, the Leibniz Institute for Photonic Technologies (Leibniz-IPHT) and the University of Ulm were inspired by nature. This is where the most effective storage of sunlight takes place in chemical bonds in photosynthesis. In the chloroplasts, the light-harvesting and reaction complexes are firmly arranged in the thylakoid membrane. The researchers in the group headed by Prof. Dr. Felix Schacher with the help of polymers that interact with both hydrophilic and hydrophobic substances. These charged graft copolymers are manufactured artificially.

Organic dyes, more than an alternative

While most approaches to artificial photosynthesis rely on noble metal complexes as light-absorbing materials, the working group of Prof. Dr. Kalina Peneva worked on metal-free dyes. The Jena scientists rely on 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 fraction of the earth’s crust and are therefore limited in perspective, ” explains Prof. Dr. Kalina Peneva. The use of photoactive compounds based on organic chemistry is much more sustainable than the use of heavy metals.

Spectroscopy – a molecular magnifying glass

However, the absorption of light alone does not produce hydrogen. To do this, the energy levels of the dyes and catalyst molecules must match each other precisely after absorption. In order to determine these energy levels, the researchers in the working group led by Prof. Dr. Benjamin Dietzek of spectroscopic methods in which conclusions can be drawn about the energy absorbed and remaining in the molecule from the interaction of matter with defined light.

Interdisciplinary cooperation solves the problems of the future

In addition to scientific knowledge, it has also been shown that the problems of the future can be tackled most effectively with interdisciplinary cooperation. In addition to organic chemists and polymer researchers, physical chemists from Leibniz-IPHT and inorganic chemists and chemical engineers from Ulm University also made valuable contributions and insights.

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