Electrodriven Chemical Looping Ammonia Synthesis Mediated by Lithium Imide

The chemical looping process for ammonia synthesis (CLAS) has advantages in avoiding competitive adsorptions of nitrogen and hydrogen and optimizing the thermodynamics and kinetics of a reaction step by step. Nitrogen carriers with favorable thermodynamic and kinetic properties are critical for such a process, especially under mild conditions. Recent studies have shown that alkali-and alkaline earth-metal imides are attractive nitrogen carriers; however, the equilibrium concentration of NH3 in the hydrogenation of imides to ammonia and hydrides is low at atmospheric pressure. Moreover, the reaction rate of nitrogen fixation on the hydrides is slow. Here, we show that an electrodriven CLAS (ECLAS) mediated by a lithium imide is feasible in a LiCl-NaCl-KCl eutectic electrolytic cell with a nickel foam electrode. We demonstrate that the reactions of lithium imide hydrogenation and lithium hydride nitridation are both promoted by the input of electric energy. The average ammonia production rate over such an electrodriven CLAS is ca. 8 times higher than that of a thermal-driven CLAS.