Prof. Dr. Roland Marschall at the apparatus for gas-phase photocatalysis in his Bayreuth laboratory for physical chemistry Photo: UBT / Chr. Wißler.
For more than a hundred years, the chemical industry has been using the Haber-Bosch process to obtain industrially usable nitrogen. Around 180 million tonnes of ammonia (NH₃) are produced synthetically in this way every year. It is used for the production of fertilisers, but also, for example, for refrigerants and plastics. However, the process consumes a lot of energy and the CO₂ emissions are high. Indeed, the process causes about one percent of annual greenhouse gas emissions worldwide. As a consequence, the priority programme "Nitroconversion" aims to develop fundamentally new methods of more sustainable nitrogen production. Essential aspects here are the climate-friendly use of renewable energies and the optimisation of value chains. The programme is thus also contributing to the United Nations Sustainable Development Goals.
One of the new projects at the University of Bayreuth deals with the basics and the development of a new process enabling efficient, cost-effective, and demand-oriented ammonia production. Developing countries could thereby be enabled to produce nitrogenous fertilisers for nutrient-poor soils. Prof. Dr. Roland Marschall is cooperating in this project with Prof. Dr. Barbara Milow at the Institute of Materials Research at the German Aerospace Centre in Cologne, and with Prof. Dr. Dirk Ziegenbalg at the Institute of Chemical Engineering at the University of Ulm. The process envisaged involves loading nanostructured semiconductors (TiO₂ aerogels) with electrons through light irradiation. These semiconductors are then discharged in the dark with nitrogen molecules (N₂) to produce ammonia. "Our goal in this project is to produce ammonia on demand at all times. Further steps will involve developing a concept for a new type of reactor with which this on-demand production can take place in a decentralised manner and without great technological investment. While the Haber-Bosch process relies on large centralised industrial plants, our alternative path relies on flexible fertiliser production on site," says Prof. Dr. Roland Marschall, who is Chair of Physical Chemistry III at the University of Bayreuth.
However, the priority programme is explicitly not limited to novel ways of synthesising ammonia. It starts with the fundamental challenge that nitrogen occurs in nature almost exclusively in the form of N₂ molecules. In these, two nitrogen atoms are coupled by an extraordinarily strong triple bond. This bond must be broken so that nitrogen becomes available for the production of fertilisers and other everyday products.
Against this background, the second research project at the University of Bayreuth deals with a specific but central aspect of nitrogen production: the catalytic reduction of N₂. The natural model is enzyme complexes, so-called nitrogenases, which are to be imitated and possibly even surpassed by novel catalyst materials. The research work aims to develop suitable electrodes and electrolyte combinations that are optimally suited to initiate the desired electro- and photoelectrocatalytic reactions. The research also involves new electrospinning technologies to test hybrid electrolytes where ionic liquids are fixed on and within fibrous structures. In this second project, Prof. Dr. Roland Marschall is cooperating with engineering scientist Prof. Dr.-Ing. Christina Roth from Bayreuth and with Prof. Dr. Andrea Balducci at the Faculty of Chemical and Earth Sciences at Friedrich Schiller University in Jena.
"The priority programme with its total of eleven sub-projects offers a unique opportunity to get to the bottom of the prerequisites for sustainable nitrogen production in close multi- and interdisciplinary cooperation, and to provide concepts for this that can be implemented flexibly and cost-effectively. In total, 21 universities and research institutions are involved in SPP 2370. We will work towards developing practicable solutions mindful of climate protection, energy efficiency, and resource conservation, which are not necessarily addressed by the high-tech prerequisites of western industrialised countries. The current threat of food crisis as a result of drastically reduced fertiliser and grain exports shows the urgency of the challenges that we now intend to tackle together," says SPP coordinator Prof. Dr. Roland Marschall.
Contact for scientific information:
Prof. Dr. Roland Marschall
Physical Chemistry III
University of Bayreuth
Phone: +49 (0)921 55-2760
E-mail: roland.marschall@uni-bayreuth.de
