Direct recovery of electro-synthesized ammonia from low-concentration nitric oxide using pulse electrodeposited Cu/C catalyst in a catholyte-free system

Electrochemical production of ammonia (NH₃) from nitric oxide (NO) offers a sustainable and environmentally friendly way to convert a nitrogenous pollutant into a valuable chemical feedstock and energy carrier. However, practical challenges in the electrochemical NO-to-NH₃ conversion stem from mass transport limitations due to low NO concentrations in real-world streams and the need for post-purification of synthesized NH₃. In this study, by synergistically developing an electrocatalyst (pulse-electrodeposited copper) and implementing a catholyte-free cell configuration with advantages of (i) facile NO transport, (ii) inhibited side reaction, and (iii) direct NH₃ recovery in an external acid, we showcase an NH₃ Faradaic efficiency of 85.6 % and a production rate of 53.4 μmol cm⁻²h⁻¹ starting from 500 ppm NO. Crucially, the electro-synthesized NH₃ was directly recovered as a high-purity aqueous ammonium sulfate solution comparable to industrial-grade quality. This approach opens the door to transforming waste into resources in a more energy-efficient and straightforward manner.