Goyal Ishita, Gande Vamsi V, Bhawnani Rajan R, Hamlyn Rebecca, Farghaly Ahmed A, Singh Meenesh R
Department of Chemical Engineering, University of Illinois Chicago, Chicago, Illinois, 60607, United States.
Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, United States.
Adv Sci (Weinh). 2025 Jul;12(28):e2504882. doi: 10.1002/advs.202504882. Epub 2025 May 15.
Metal-mediated electrochemical synthesis of ammonia (NH) is a promising method to activate N at room temperature. While a Li-mediated approach has been optimized to produce NH at high current density and selectivity, Li's scarcity and its highly negative plating potential limit scalability and energy efficiency. Alternative mediators have been proposed, but only Ca has shown some promise, achieving ≈50% Faradaic efficiency (FE), though requiring voltages beyond -3 V. Here, we report a Mg-mediated nitrogen reduction reaction (Mg-NRR), where N is activated on Mg to form MgN, followed by protolysis to release NH and regenerate Mg. A notable NH FE of 25.28 ± 3.80% is achieved at a current density of -45 mA cm, corresponding to an NH partial current density of -11.30 ± 1.77 mA cm under 6 bar N. Isotope-labeled experiments confirm that NH originates from N, with similar FE (25.15 ± 1.01%). Importantly, NH production is demonstrated at a total cell potential as low as -3 V. This Li-free Mg-NRR system offers key advantages, including lower energy input and use of earth-abundant materials, making it a scalable route for sustainable NH synthesis.
金属介导的电化学合成氨是一种在室温下活化氮气的有前景的方法。虽然锂介导的方法已得到优化，能够在高电流密度和选择性下生产氨，但锂的稀缺性及其极高的负镀覆电位限制了其可扩展性和能源效率。人们已提出了替代介导剂，但只有钙显示出了一定的前景，实现了约50%的法拉第效率（FE），不过所需电压超过 -3 V。在此，我们报道了一种镁介导的氮还原反应（Mg-NRR），其中氮气在镁上被活化形成MgN，随后通过质子解作用释放氨并使镁再生。在电流密度为 -45 mA cm² 时，实现了显著的氨法拉第效率25.28 ± 3.80%，在6 bar氮气压力下，对应的氨分电流密度为 -11.30 ± 1.77 mA cm²。同位素标记实验证实氨源自氮气，法拉第效率相似（25.15 ± 1.01%）。重要的是，在低至 -3 V的总电池电位下证明了氨的产生。这种无锂的Mg-NRR系统具有关键优势，包括更低的能量输入和使用储量丰富的材料，使其成为可持续氨合成的可扩展途径。
