Present ammonia synthesis, via the Haber-Bosch process, occurs in centralised facilities above 150 bar and above 400 C; it consumes a colossal 1% of our global fossil fuel consumption. Electrolytic ammonia synthesis, i.e. below 100 C and at atmospheric pressures, could be far more attractive: it would be powered by renewable energy and would take place at the point-of-consumption. However, since nitrogen gas is incredibly inert, it is intrinsically very challenging to catalyse its conversion to ammonia. Only the most reactive metal or metal nitride surfaces bind to dinitrogen. Such surfaces will preferentially react to other species, such as hydrogen or oxygen from water or air. Catalysing the reaction requires a system which constrains access to oxygen, hydrogen and water but facilitates access to nitrogen.
My aim for NitroScission is to elucidate pathways —at a molecular level— to catalyse the reaction at high efficiency using solid electodes.
To date, the only solid surface capable of reducing nitrogen to ammonia is lithium electrodeposited in an organic electrolyte. While it was first discovered in the 1990s in Japan, it was only 2019 did my colleagues and I provide irrefutable evidence that the reaction actually takes place. Since then, enormous progress has been made to the rate and efficiency of the reaction. Nonetheless, electrochemical nitrogen reduction is still a highly nascent field, and there is ample space for improvement before it can become a technological reality. In particular, we still lack insight into why the lithium mediated system works and how it could be improved further.
For Nitroscission, my team is combinign electrochemical tests, operando and ex-situ spectroscopy and microscopy to establish (a) what makes the lithium mediated system unique (b) how to optimise the lithium mediated system and (c) how can we move beyond lithium based electrodes.
