Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark.
J Phys Chem Lett. 2022 May 26;13(20):4605-4611. doi: 10.1021/acs.jpclett.2c00768. Epub 2022 May 19.
Although oxygen added to nonaqueous lithium-mediated electrochemical ammonia synthesis (LiMEAS) enhances Faradaic efficiency, its effect on chemical stability and byproducts requires understanding. Therefore, standardized high-resolution gas chromatography-mass spectrometry and nuclear magnetic resonance were employed. Different volatile degradation products have been qualitatively analyzed and quantified in tetrahydrofuran electrolyte by adding some oxygen to LiMEAS. Electrodeposited lithium and reduction/oxidation of the solvent on the electrodes produced organic byproducts to different extents, depending on the oxygen concentration, and resulted in less decomposition products after LiMEAS with oxygen. The main organic component in solid-electrolyte interphase was polytetrahydrofuran, which disappeared by adding an excess of oxygen (3 mol %) to LiMEAS. The total number of byproducts detected was 14, 9, and 8 with oxygen concentrations of 0, 0.8, and 3 mol %, respectively. The Faradaic efficiency and chemical stability of the LiMEAS have been greatly improved with addition of optimal 0.8 mol % oxygen at 20 bar total pressure.
尽管向非水锂介导的电化学氨合成（LiMEAS）中添加氧气可以提高法拉第效率，但需要了解其对化学稳定性和副产物的影响。因此，采用了标准化的高分辨率气相色谱-质谱和核磁共振技术。通过向 LiMEAS 中添加一些氧气，对四氢呋喃电解质中的一些挥发性降解产物进行了定性和定量分析。在不同的氧气浓度下，电极上的锂沉积和溶剂的还原/氧化会产生不同程度的有机副产物，导致添加氧气后 LiMEAS 的分解产物减少。固体电解质中间相的主要有机成分是聚四氢呋喃，通过向 LiMEAS 添加过量的氧气（3 mol%）可以将其去除。在氧气浓度分别为 0、0.8 和 3 mol%的情况下，检测到的副产物总数分别为 14、9 和 8。在 20 巴总压力下添加最佳的 0.8 mol%氧气可以大大提高 LiMEAS 的法拉第效率和化学稳定性。
