Fast, in-situ, real-time detection of ammonia in continuous electrochemical nitrogen reduction Artem Khobnya , Bethan Davies, Daisy Thornton, Ifan Stephens Imperial College, UK Ammonia is a globally important molecule, it is mainly used as fertiliser, however, in the future, demand for ammonia could increase significantly as it could be used as a hydrogen storage molecule or even a green fuel. Developing continuous electrochemical nitrogen reduction to ammonia, as opposed to the currently utilised Haber-Bosch process, would allow ammonia production to be carried out at ambient conditions, be decentralised and not be dependent on fossil fuels. Despite its feasibility, ambient pressure electrochemical nitrogen reduction remains inefficient, unstable and poorly understood. The key to solving these issues is understanding the electrochemical reactions that govern this system, many of which involve gases and volatile species. Electrochemistry-Mass Spectrometry is a powerful technique that allows gases/volatile species evolved during electrochemical reaction to be monitored quantitatively in real-time. One of the main challenges of this system, however, is the detection of ammonia. While the detection of ammonia using this technique has been reported 1 , it required several compromises: namely soft ionisation (which reduces signal to noise ratio) and heating of the chamber walls which increases complexity. In this work, a unique system was developed that allowed ammonia detection without the use of soft ionisation or chamber heating. This was achieved by placing the entire system into an argon glovebox and using an optimised electrochemical cell, originally developed for lithium batteries. This reduced water in the system to a previously unobtainable level (on the order of ppm), which eliminates the interference with ammonia detection. Furthermore, the lack of water was found to reduce ammonia’s adsorption strength, eliminating the need for chamber heating while decreasing ammonia signal latency significantly. While significant improvements to efficiency have been recently achieved using electrolyte optimisation 2 , the ability to detect ammonia with a higher signal to noise ratio and much faster response times achieved in this work provides a strong foundation for investigating the effect of dynamic operating conditions on the performance of continuous electrochemical nitrogen reduction. References 1. Krempl, K., Hochfilzer, D., Cavalca, F., Saccoccio, M., Kibsgaard, J., Vesborg, P.C.K. &; Chorkendorff, I. (2022) Quantitative Operando Detection of Electro Synthesized Ammonia Using Mass Spectrometry. ChemElectroChem . 9 (6). doi:10.1002/ celc.202101713. 2. Du, H.-L., Chatti, M., Hodgetts, R.Y., Cherepanov, P.V., Nguyen, C.K., Matuszek, K., MacFarlane, D.R. &; Simonov, A.N. (2022) Electroreduction of nitrogen with almost 100% current-to-ammonia efficiency. Nature (London) . 609 (7928), 722–727. doi:10.1038/s41586-022-05108-y.
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