Continuous ammonia electrosynthesis from nitrogen and water from a membrane-based flow cell

Continuous electrochemical lithium-mediated ammonia production has shown promising performance. For this reaction, using protons generated from water oxidation would provide a direct route for proton supply, eliminating the need to generate molecular hydrogen. However, recent studies reported low Faradaic efficiency to ammonia when using water directly as a proton source. In this work, we integrate an electrically isolated Pd membrane to transfer protons generated from water oxidation into a non-aqueous lithium-mediated nitrogen reduction system. By employing Pd as a proton- and electron-conducting membrane rather than solely as a cathode, we enabled continuous operation in a flow-cell configuration, achieving a Faradaic efficiency of 40 ± 3% at a current density of –6 mA cm⁻² over 6 hours. Operando mass spectrometry confirmed that the produced ammonia contained protons generated by water oxidation. This approach of using Pd provides a practical strategy for proton transport and establishes a viable device configuration for advancing electrochemical lithium-mediated nitrogen reduction toward sustainable green ammonia synthesis.