Probing N 2 reduction intermediaries using in situ in operando enhanced IR spectroscopy Johannes Rietbrock 1 , Matthew Spry 1 , Yu Katayama 2 , Johannes Lischner 1 , Fang Xie 1 , Ifan E.L. Stephens 1 1 Imperial College London, UK, 2 Osaka University, Japan Electrochemical ammonia synthesis is a promising pathway to carbon neutral fertiliser production as well as opening opportunities for ammonia use as a hydrogen vector and, in turn, energy store. The lithium mediated system is to date the only rigorously verified ammonia reduction pathway (1)(2). Whilst rapid advancements in the optimisation of system parameters is leading to increased faraday efficiency and ammonia yield, fundamental understanding of the mechanism behind nitrogen reduction is lacking. In situ in operando surface enhanced IR spectroscopy will provide insight into the mechanism for nitrogen reduction in addition to helping decodify the structure of the SEI. The SEI is thought to be vital in regulating diffusion of reactants to the active sites (3)(4). So far, this technique has only been implemented in a qualitative manner. Developing a method to control the nanostructures needed for surface enhancement will allow for the probing of specific wavelengths making the determination of reaction intermediaries possible. In turn, an accurate molecular picture of the surface chemistry can be developed providing insight into the factors affecting nitrogen reduction. The size and shape of gold nanoparticles can be tailored to increase surface enhancement. If delamination problems can be overcome, these nanoparticles could provide greater surface enhancement through optimising morphology for certain wavelengths. Nanoscale surface roughness could allow reactions to take place between nanoparticles further increasing enhancement. References 1. Andersen SZ, Čolić V, Yang S, Schwalbe JA, Nielander AC, McEnaney JM, et al. A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature [Internet]. 2019;570(7762):504–8. 2. Available from: https://doi.org/10.1038/s41586-019-1260-xChoi J, Suryanto BHR, Wang D, Du HL, Hodgetts RY, Ferrero Vallana FM, et al. Identification and elimination of false positives in electrochemical nitrogen reduction studies. Nat Commun [Internet]. 2020;11(1):5546. 3. Available from: https://doi.org/10.1038/s41467-020-19130-zLi K, Andersen SZ, Statt MJ, Saccoccio M, Bukas VJ, Krempl K, et al. Enhancement of lithium-mediated ammonia synthesis by addition of oxygen. Science (1979) [Internet]. 2021;374(6575):1593–7. 4. Available from: https://www.science.org/doi/abs/10.1126/science.abl4300Westhead O, Spry M, Bagger A, Shen Z, Yadegari H, Favero S, et al. The role of ion solvation in lithium mediated nitrogen reduction. J Mater Chem A Mater [Internet]. 2023; Available from: http://xlink.rsc.org/?DOI=D2TA07686A
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