A practical way to enhance the synthesis of N8- from an N3- precursor, studied by both computational and experimental methods.

Polymeric nitrogen (PN) belongs to a general family of materials containing all-nitrogen molecules or clusters. Although it is rare and challenging to synthesize PN members, they are attracting increasing scientific attention due to their high energy storage capacity and possible use as a green catalyst. A few theoretical calculations predicted the possible PN phases from N2 gas, but they all require extremely high pressures and temperatures to synthesize. In this work, a practical way to synthesize N8 polymeric nitrogen from an N3− precursor is elucidated using density functional theory calculations. The detailed mechanism, , is determined. The calculated energy barriers indicate that the first step is the rate-limiting step. This result guides us to rationally synthesize N8 under UV (254 nm) irradiation, chosen based on the calculated absorption spectrum for the azide anion. As expected, UV irradiation enhances N8 yields by nearly four times. This provides an interesting route to the scalable synthesis of high energy density N8 compounds.