Iron-sulfur gel provides new route to ammonia

Abstract

To produce the large quantities of fertilizer needed to sustain global food production, industry relies on the Haber-Bosch process to split dinitrogen from the air to synthesize ammonia. But to generate the high temperatures and pressures needed for the reaction, ammonia plants consume fossil fuels and, as a result, contribute significantly to greenhouse gas emissions. Researchers want to develop a green alternative to the Haber-Bosch process. In a new effort, Mercouri G. Kanatzidis and George C. Schatz of Northwestern University and coworkers used iron-sulfur (Fe4S4) clusters, found naturally in the nitrogenase enzymes bacteria use to split dinitrogen, to make a light-driven catalyst that converts N2 to NH3 in water at ambient temperature and pressure (Proc. Natl. Acad. Sci. USA 2016, DOI: 10.1073/pnas.1605512113). After synthesizing the Fe4S4 clusters, the researchers link them with [Sn2S6]4– anions and form the complex into a chalcogel, a foamy gel containing the chalcogen element sulfur. The