1e:T420,NO removal from exhausted gas is necessary owing to its damage to environment. Meanwhile, the electrochemical ammonia synthesis (EAS) from N₂ suffers from low reaction rate and Faradaic efficiency (FE). Now, an alternative route for ammonia synthesis is proposed from exhaust NO via electrocatalysis. DFT calculations indicate electrochemical NO reduction (NORR) is more active than N₂ reduction (NRR). Via a descriptor-based approach, Cu was screened out to be the most active transition metal catalyst for NORR to NH₃ owing to its moderate reactivity. Kinetic barrier calculations reveal NH₃ is the most preferred product relative to H₂ , N₂ O, and N₂ on Cu. Experimentally, a record-high EAS rate of 517.1 μmol cm^-2 h^-1 and FE of 93.5 % were achieved at -0.9 V vs. RHE using a Cu foam electrode, exhibiting stable electrocatalytic performances with a 100 h run. This work provides an alternative strategy to EAS from exhaust NO, coupled with NO removal.1f:T41a,Nitrate reduction on Cu (100) and Cu (111) surfaces in alkaline and acidic solutions was studied by electrochemical methods (cyclic voltammetry, rotating disc electrode) coupled with online and in situ characterization techniques (mass spectrometry, ion chromatography and Fourier transformed infra-red spectroscopy) to evaluate the reaction mechanism and products on the different surfaces. Electrochemical results show that reduction of nitrate in alkaline media on Cu is structure sensitive. The onset potential on Cu (100) is +0.1 V vs. RHE, ca. 50 mV earlier than on Cu (111). The onset potentials for nitrate reduction on Cu (100) and Cu (111) in acidic media are rather similar. Analytical techniques show a diverse product distribution for both surfaces and for both electrolytes. Whereas in acidic media both Cu electrodes show the formation of NO and ammonia, in alkaline media Cu reduces nitrate to nitrite and further to hydroxylamine. In alkaline media, Cu (100) is a more active surface for the formation of hydroxylamine than Cu (111).

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