Periodic Reporting for period 2 - NitroScission (Electrochemical scission of dinitrogen under ambient conditions)
Periodo di rendicontazione: 2022-07-01 al 2023-12-31
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.
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.
For the first period of the project, the main activities have focussed on (i) optimising newequipment (ii) developing new methodologies to probe nitrogen reduction (iii) benchmarking electrochemical test data (iii) probing sensitivity to key parameters, e.g. salt concentration and impurities.
Our major achievements to date have been:
a) developed a new method based on mass spectrometry capable of measuring hydrogen and ammonia produced in organic electolytes from solid electrodes with unprecedented sensitivity and in real time. We are currently using this method to explore how to use dynamic effects to tailor the reaction kinetics.
(b) Using the method described in b, as a side project we also discovered we could use it to probe undesired gas evolution formed during the degradation of lithium (and sodium) ion batteries. We have observed degradation processes that had previously been overlooked by other scientists using less sensitive methods. The ensuing insight will enable longer lasting batteries to be engineered. We have filed a patent application for our invention and it is already being commercialised and sold to battery material manufacturers.
(c) We quantified the potential energy losses in lithium mediated nitrogen reduction. We found the vast majority are due to the electrodeposition of lithium.
(d) We discovered that small changes in the concentration of the lithium salt, ethanol concentration and water content can make enormous improvements to the efficiency and stability of the reaction. This gives us hope that there is plenty of scope for engenderign further improvements to the reaction.
(e) we identified using a combination of theoretical calculations and experiments that other electrodes, could, in princpile, reduce nitrogen to ammonia, aside from lithium. For instance, our analysis suggests that magnesium could work even better than ltihium and be less constrained by supply constraints.
Our major achievements to date have been:
a) developed a new method based on mass spectrometry capable of measuring hydrogen and ammonia produced in organic electolytes from solid electrodes with unprecedented sensitivity and in real time. We are currently using this method to explore how to use dynamic effects to tailor the reaction kinetics.
(b) Using the method described in b, as a side project we also discovered we could use it to probe undesired gas evolution formed during the degradation of lithium (and sodium) ion batteries. We have observed degradation processes that had previously been overlooked by other scientists using less sensitive methods. The ensuing insight will enable longer lasting batteries to be engineered. We have filed a patent application for our invention and it is already being commercialised and sold to battery material manufacturers.
(c) We quantified the potential energy losses in lithium mediated nitrogen reduction. We found the vast majority are due to the electrodeposition of lithium.
(d) We discovered that small changes in the concentration of the lithium salt, ethanol concentration and water content can make enormous improvements to the efficiency and stability of the reaction. This gives us hope that there is plenty of scope for engenderign further improvements to the reaction.
(e) we identified using a combination of theoretical calculations and experiments that other electrodes, could, in princpile, reduce nitrogen to ammonia, aside from lithium. For instance, our analysis suggests that magnesium could work even better than ltihium and be less constrained by supply constraints.
In the remainder of the project, we would like to use detailed characterisation methods, including cryo-microscopy, infrared spectroscopy and electrochemistry mass spectrometry to pinpoint the exact features that enable lithium to transform nitrogen to ammonia so well. The ensuing insight will allow us to reverse engineer electrode-electrolyte interfaces so that we can produce more tailored systems for reducing nitrogen to ammonia. We also anticipate that we will be able to realise some of our theoretical predictions that other systems are capable of reducing nitrogen to ammonia with superior perfromance to the current state of the art.