The activation of N₂ is very important in the industrial synthesis of ammonia for the production of nitrogen fertilizer, which is vital for modern agriculture. Due to the stability of N₂, this usually requires transition-metal-based catalysts and harsh conditions. The development of methods for N₂ activation under mild conditions and without transition metals would be useful to realize more environmentally friendly processes.

Zhujun Zhang, Masaaki Kitano, Tokyo Institute of Technology, Yokohama, Japan, Hideo Hosono, Tokyo Institute of Technology and National Institute for Materials Science, Tsukuba, Japan, and colleagues have found that a 2D electride of Ba₂N with electrons in the interlayer spaces can be used for the transition-metal-free dissociation of N₂ under mild conditions. An electride is an ionic compound in which an electron serves as an anion. In layered 2D electrides, atomically thin layers of electrons and ionized atoms alternate.

The team prepared Ba₂N by heating Ba metal in an N₂ flow under ambient pressure at elevated temperatures. They confirmed that Ba₂N has a high efficiency for N₂ dissociation using an N₂ isotopic exchange reaction with ¹⁵N₂ and ¹⁴N₂, which can be monitored using mass spectrometry. The 2D Ba₂N electride promotes N₂ dissociation with a very small activation energy of 35 kJ mol^–1. The team found evidence for the formation of an (N₂)^2– anion, a diazenide, as an intermediate in the interlayer space of Ba₂N. 

• A 2D Ba₂N Electride for Transition Metal-Free N₂ Dissociation under Mild Conditions,
  Zhujun Zhang, Yihao Jiang, Jiang Li, Masayoshi Miyazaki, Masaaki Kitano, Hideo Hosono,
  J. Am. Chem. Soc. 2023.
  https://doi.org/10.1021/jacs.3c09362