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.