Global ammonia production from dinitrogen happens via two dominating processes: the natural enzymatic process catalyzed by nitrogenase, which occurs at ambient temperature and atmospheric pressure, and the industrial Haber-Bosch process, which occurs at high temperatures and pressures. This latter process currently consumes approximately 1 % of the world’s total energy per year. Lower energy routes to NH₃ synthesis would be useful.

Louise A. Berben and colleagues, University of California, Davis, USA, have developed a transition-metal-free electrochemical reduction of N₂ into NH₃, using an aluminium complex (pictured in white). This complex facilitates NH₃ production at a low reduction potential of –1.2 V measured vs. a saturated calomel electrode (SCE).

The reaction occurs under 1 atm of N₂ when the twice-protonated Al(III) complex is reduced by two electrons (pictured). Sub-stoichiometric quantities of NH₃ are generated. This work provides new ideas for strategies, reaction mechanisms, and catalysts derived from main group elements and redox active ligands which could be used to mediate small-molecule transformations.

• Electrochemical Reduction of N₂ to NH₃ at Low Potential by a Molecular Aluminum Complex,
  Tobias J. Sherbow, Emily J. Thompson, Amela Arnold, Richard I. Sayler, R. David Britt, Louise A. Berben,
  Chem. Eur. J. 2018.
  https://doi.org/10.1002/chem.201804454