Electro-synthesis of Ammonia from Dilute Nitric Oxide on a Gas Diffusion Electrode

Abstract

The electrochemical conversion of nitric oxide (NO) to ammonia (NH3) provides a sustainable route to transform an air pollutant into a value-added chemical. However, the development of NO electroreduction remains hindered by the poor solubility in aqueous electrolytes, requiring the use of concentrated NO. Here, we report a dilute NO reduction using a gas diffusion electrode (GDE) to circumvent the mass transport issue. Through the incorporation of nanoscale zero-valent iron into carbon black on the GDE, 96% NH3 Faradaic efficiency was achieved with 1% NO, and the computational calculations revealed that the Fe catalyzed the breaking of the N–O bond in the H2NO intermediate. The NH3 production rate was accelerated by controlling the concentration of protons in the electrolyte and reached 1239 μmol cm–2 h–1 with 10% NO. Our findings show that the gas-phase electrolysis of dilute NO can offer a practical option for upcycling the waste nitrogen.