Lithium-mediated electrochemical nitrogen reduction: Mechanistic insights to enhance performance

• Published in: iScience 2021-10, Vol.24 (10), p.103105-103105, Article 103105
• Main Authors: Cai, Xiyang, Fu, Cehuang, Iriawan, Haldrian, Yang, Fan, Wu, Aiming, Luo, Liuxuan, Shen, Shuiyun, Wei, Guanghua, Shao-Horn, Yang, Zhang, Junliang
• Format: Article
• Language: English
• Subjects: Chemical reaction; Chemical synthesis; Electrochemistry
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2021.103105

Green synthesis of ammonia by electrochemical nitrogen reduction reaction (NRR) shows great potential as an alternative to the Haber-Bosch process but is hampered by sluggish production rate and low Faradaic efficiency. Recently, lithium-mediated electrochemical NRR has received renewed attention due to its reproducibility. However, further improvement of the system is restricted by limited recognition of its mechanism. Herein, we demonstrate that lithium-mediated NRR began with electrochemical deposition of lithium, followed by two chemical processes of dinitrogen splitting and protonation to ammonia. Furthermore, we quantified the extent to which the freshly deposited active lithium lost its activity toward NRR due to a parasitic reaction between lithium and electrolyte. A high ammonia yield of 0.410 ± 0.038 μg s−1 cm−2 geo and Faradaic efficiency of 39.5 ± 1.7% were achieved at 20 mA cm−2 geo and 10 mA cm−2 geo, respectively, which can be attributed to fresher lithium obtained at high current density. [Display omitted] •Characteristics of nitrogen splitting and protonation processes are clarified•Parasitic reactions between metallic lithium and tetrahydrofuran are revealed•Fresh lithium model is employed to rationalize performance dependence on current•Top-level ammonia yield of 0.410 μgNH3 s−1 cm−2 geo is achieved Chemical reaction; Electrochemistry; Chemical synthesis