This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Two nearly identical materials have completely different chemical behavior. Research teams at the University of Vienna and TU Wien studied catalysts that use the energy of sunlight to produce ammonia.
Surprisingly, when the three iron atoms that form tiny triangles in these catalysts are replaced by chromium atoms, the chemical reaction no longer takes place. The teams have now explained why. Iron and chromium triangles have very different magnetic properties, and these magnetic properties also reveal whether the material works as a catalyst.
The findings are published in the journal ACS Energy Letters. Both research teams belong to the FWF Cluster of Excellence MECS (Materials for Energy Conversion and Storage), which develops new materials for the energy transition. Ammonia is indispensable for humanity.
Fertilizers made from ammonia help feed a large part of the world's population. However, the industrial production of ammonia from nitrogen and hydrogen usually requires high temperature and high pressure, which makes it extremely energy-intensive. Researchers are therefore working on an alternative that needs less energy.
Photocatalysts are special new materials that absorb sunlight and use its energy to turn nitrogen into ammonia. "Metal-organic frameworks are promising candidates," says Jana Bischoff (TU Wien). "These are crystals that contain small cavities.
Their framework consists of nodes with metal atoms, which are connected by organic molecules." The team studied a structure called MOF MIL-101. At each node, three metal atoms are arranged in a triangle around a central oxygen atom. This structure can be made with different kinds of metal atoms without changing the framework.
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