(Keynote) Why Is Lithium Uniquely Able to Reduce Nitrogen to Ammonia Under Ambient Conditions?

Abstract

There is a burgeoning interest in the development of a green method of ammonia synthesis; ammonia, already critical for fertilizers in the agricultural industry, is also being touted as a possible future energy vector or carbon-free fuel. The current method of production - the Haber Bosch process - is highly environmentally damaging and energy intensive but to date no viable alternative has been demonstrated. An electrochemical method operating under ambient conditions would be particularly attractive, as it would enable ammonia to be produced on a decentralised basis on-site and on-demand.1 Thus far, amongst solid electrodes, only lithium based electrodes in organic electrolytes can unequivocally reduce nitrogen to ammonia.2 Even so, at present, the lithium based system is far too inefficient for practical uses; moreover, it is highly unstable.In the current contribution, we will explore the underlying reasons why lithium is unique in its ability to reduce nitrogen to ammonia. We use a combination of electrochemical experiments, Raman spectroscopy, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and density functional theory. By drawing from the adjacent fields of enzymatic nitrogen reduction and battery science, we will aim to build a holistic picture of the factors controlling nitrogen reduction.1 Nilsson, A. & Stephens, I. E. L. in Research needs towards sustainable production of fuels and chemicals (eds J.K. Nørskov, A. Latimer, & C. F. Dickens) 49 (Energy-X, Brussels, Belgium, 2019).2 Andersen, S. Z., Colic, V., Yang, S., Schwalbe, J. A., Nielander, A. C., McEnaney, J. M., Enemark-Rasmussen, K., Baker, J. G., Singh, A. R., Rohr, B. A., Statt, M. J., Blair, S. J., Mezzavilla, S., Kibsgaard, J., Vesborg, P. C. K., Cargnello, M., Bent, S. F., Jaramillo, T. F., Stephens, I. E. L., Norskov, J. K. & Chorkendorff, I. Nature 570, 504, (2019).