A research team from Ulm University and the University of Jena has been successful in significantly advancing the development of solar-powered catalysts. Their optimised photocatalysts are more effective than conventional thermal catalysts and thus provide a basis for the sustainable use of regenerative energy forms in the chemical industry. The advantage is that no major investments are required in order to convert the conventional processing methods to ones that are solar-based.

Around 80 per cent of all chemical products are produced with the help of catalytic processes. Catalysts accelerate chemical reactions or get them started by reducing the so-called activation energy. This task is often performed by thermal catalysts, the use of which entails fossil fuel consumption. However, sunlight can also be used effectively for catalytic processes. Researchers from Ulm University and the University of Jena have recently provided proof of this. They have been successful in optimising a solar-powered photocatalyst in such a way that it is able to work faster and more efficiently than a conventional thermal catalyst. “This development opens up the door for a sustainable solar future for the chemical industry”, says Professor Sven Rau, head of the Institute of Inorganic Chemistry I at Ulm University.

The local chemist coordinated a study in collaboration with his colleague from Jena, Professor Benjamin Dietzek- Ivanšić, which impressively demonstrates the performance of photocatalysts. “We were able to show that the design of the catalyst plays a decisive role for the speed of the light reaction taking place – but not for the thermal reaction”, explains Dietzek-Ivanšićv, who performs research at the Institute of Physical Chemistry at the University of Jena and heads the Department of Functional Interfaces at the Leibniz Institute of Photonic Technologies. The photocatalyst currently being studied consists of three chemically active components: a centre for the absorption of light energy, a bridge and a catalysis centre. “We were surprised to discover in the course of our experiments that the structure of the bridge has a particularly critical impact on the efficiency of the catalyst”, relate the first authors of the study Dr Linda Zedler (University of Jena) and Pascal Wintergerst (Ulm University). With the help of chemical synthesis, catalytic studies and ultra-fast spectroscopy, the research team was able to identify in detail the processes taking place.

The study, published in Nature Communications, demonstrates that such solar-powered photocatalysts are suitable for producing high-energy, high-quality reaction products out of low-energy source materials. If conventional thermal catalysts are used, the source materials need to have a higher level of energy in order to achieve comparable reactions.

Proof from an example with biotechnological significance

Proof for this was provided by the chemists for an application example with great biotechnological potential: the hydrogenation of nicotinamide, which results in the generation of an energy-rich molecule with extensive possibilities for application. The organic compound nicotinamide is a central component of nicotinamide adenine dinucleotide (NAD+ or NADH). This coenzyme is involved in numerous metabolic redox reactions in living cells. For the researchers, the photocatalytically induced hydrogenation of nicotinamide is visible proof that solar chemistry and biotechnological applications can be paired very well.

With the blueprints for future solar-powered catalysts, established by the research team in this study, the scientists also provide basic knowledge on how to efficiently convert the energy from sunlight into chemical bonding energy and how to store it as such. This process is essential for using solar energy based on the example of nature.

“Basically, the research project also demonstrated that catalytic processes can be converted to a solar base with the help of optimised photocatalysts – and with a gain in catalytic efficiency as well”, the researchers relate. Major investments in the chemical industry are not even necessary. After all, material flows could be retained and the technological basis of the chemical process technology could continue to be used without any problems. This would be an important step for the chemical industry toward becoming more sustainable and less dependent on fossil fuels.

This project was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft – DFG) within the scope of the joint Transregio Collaborative Research Centre (SFB) 234 CataLight at Ulm University and the University of Jena. The CRC was extended for another four years at the end of May and will be receiving 12 million euros in funding. The aim of CataLight is to use sunlight to create climate-friendly energy, following the example of natural photosynthesis. Further funding comes from the German Academic Scholarship Foundation (Studienstiftung des Deuschen Volkes) PhD programmes and the Chemical Industry Fund.

Linda Zedler, Pascal Wintergerst, Alexander K. Mengele, Carolin Müller, Chunyu Li, Benjamin Dietzek-Ivanšić & Sven Rau. Outpacing conventional nicotinamide hydrogenation catalysis by a strongly communicating heterodinuclear photocatalyst. Nature Communications. https://doi.org/10.1038/s41467-022-30147-4

Text and mediacontact: Andrea Weber-Tuckermann