University of Bayreuth Energy Storage With Nitrogen

Ausschnitt aus der Kristallstruktur von FeN₄. Stickstoffatome sind blau, Eisenatome braun.
Detail of the crystal structure of FeN₄. Nitrogen atoms are blue, iron atoms brown.

Polymer chains of nitrogen have an unusually high energy density and open up new perspectives for energy storage and transmission technologies. Researchers at the University of Bayreuth have now succeeded in producing these compounds.

Nitrides are a highly interesting class of inorganic materials for research because they often have outstanding physical and chemical properties. In many cases, transition metal nitrides are characterized by extraordinary hardness, high melting points, and unusual stability. However, it is very difficult to synthesize such nitrogen compounds.

Under normal environmental conditions, nitrogen occurs mainly as a two-atomic gas N₂, which only forms chemical compounds with a few other elements. The biggest hurdle in the production of nitrogen-rich compounds is that the two nitrogen atoms of N₂ are linked by a triple bond, which must be broken at exceptionally high temperatures. How high depends on the individual cases, i.e., on the respective nitrogen-containing compound to be synthesized.

Targeted Synthesis of New Nitrogen Compounds Under High Pressure

The Bayreuth scientists have now overcome this hurdle for the first time. Using high-pressure research technologies, they have created a test environment in which the synthesis of nitrogen-rich compounds can be specifically controlled. Powdered iron and rhenium are exposed to a very high pressure and heat. The resulting compounds represent a new class of nitrogen compounds: Metal-nitrogen scaffolds.

These nitrogen compounds are of great interest for future energy research and technology, especially because they have an unusually high energy density. The energy density of ReN₈-xN₂ is many times higher than the energy density of the explosive TNT.

»The research results that we have now achieved in close international cooperation could very soon become the starting point for the development of new materials that will make a decisive contribution to the energy supply of the future. The share of renewable energies will only increase significantly if we succeed in creating sufficiently high and flexible storage capacities,« explains Prof. Dr. Leonid Dubrovinsky from the Bavarian Research  Institute of Experimental Geochemistry and Geophysics at the University of Bayreuth, who played a major role in the new studies.

The scientists report on their research results in the journals »Nature Communications« and »Angewandte Chemie«.