Lithium-mediated nitrogen reduction for ammonia synthesis: reviewing the gap between continuous electrolytic cells and stepwise processes through galvanic Li─N2 cells

Electrochemical N2 reduction reaction (E-NRR) has recently gained increasing interest within the scientific community, due to the ongoing energy crisis and pursuit of process sustainability. In this scenario, emerging lithium-mediated (Li-m) strategies are obtaining promising Faradaic efficiency (FE) and NH3 production rate values. In this work, the Li-m scenarios are classified and explained toward a more sustainable process. Continuous processes, with a lithium salt and a proton donor in an electrolytic cell, are analyzed and compared with stepwise pathways. Different parameters are summarized in relation to the system stability, for which the importance of a tailored solid electrolyte interphase (SEI) layer emerged. Among stepwise processes, the thermochemical direct nitridation of lithium is discussed together with the recently developed Galvanic Li─N2 cell strategy.