Overcoming Thermal Barrier to Magnesium Nitride Formation for Efficient Electrochemical Conversion of N ₂ and H ₂ to Ammonia at Ambient Conditions

Electrochemical nitrogen fixation mediated by magnesium offers a sustainable route to ammonia but is fundamentally limited by the high thermal barrier associated with magnesium nitride (Mg3N2) formation. Here, we demonstrate that this barrier can be overcome under ambient conditions by strategically engineering the electrolyte environment and reactor architecture. We identify salt–solvent systems that stabilize the solid electrolyte interphase (SEI) and enable continuous, reversible Mg plating, a critical prerequisite for initiating nitridation. Using in situ Raman spectroscopy, we directly monitor nitride formation kinetics of magnesium systems and compare them with those of lithium and calcium under similar conditions. To support continuous operation, we employ a nonaqueous-compatible nickel foam anode that facilitates efficient hydrogen oxidation without degradation, resolving a key challenge in closed-loop proton delivery. Through operando FTIR, isotopic labeling, and surface analysis, we confirm Mg3N2 as the active intermediate and establish a correlation between N–H bond evolution with ammonia Faradaic efficiencies of 20 ± 1.3% in flow reactors. These findings provide interesting mechanistic insights into magnesium-mediated nitrogen fixation and demonstrate a scalable pathway for electrochemical ammonia synthesis.