Lithium-mediated pathway provides a promising way for facile and selective dissociation of nitrogen for ammonia synthesis ^[1,2]. However, the prevailing electro-deposition of lithium, especially when coupled to the anodic oxygen evolution from water or hydroxide, presents disadvantages including the use of expensive Li-ion conducting ceramics^[3] or high temperature operation of molten salts^[1]. Herein, we reported a membrane-free electrochemical system for Li deposition which relies on the immiscibility of aqueous/organic electrolytes and demonstrated the applicability of the biphasic system for the realization of Li-mediated ammonia synthesis. The behavior of this system is not different from a LISICON-based cell,^[1] especially thanks to the stability of the biphasic system. Rather, this system requires lower cell voltage (5.3 V in this study vs. 6.2 V in LISICON-based cell^[3] at 5 mA cm^-2), even without the need of expensive membrane, rendering it more economically favorable. The fairly decent FE and NH₃ synthesis rate (57.2 % and 1.21 × 10^-9 mol cm^-2s^-1, respectively) have been realized merely using one hybrid model electrolytes system (LiClO₄ and PC-H₂O) without any optimization. Judicious selection of immiscible electrolytes with better biphasic stability, higher conductivity, higher stability against Li (lower SEI formation), and applicability to a continuous, integrated process will achieve further improvements in the novel Li-mediated NH₃ synthesis approach.

References:

[1] J. M. McEnaney, A. R. Singh, J. A. Schwalbe, J. Kibsgaard, J. C. Lin, M. Cargnello, T. F. Jaramillo and J. K. Nørskov, Energy & Environmental Science, 2017, 10, 1621–1630.

[2] N. Lazouski, Z. J. Schiffer, K. Williams and K. Manthiram, Joule, 2019, 3, 1127–1139.

[3] K. Kim, S. J. Lee, D.-Y. Kim, C.-Y. Yoo, J. W. Choi, J.-N. Kim, Y. Woo, H. C. Yoon and J.-I. Han, ChemSusChem, 2018, 11, 120–124.