Direct Electrochemical Ammonia Synthesis from Nitric Oxide

Abstract

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.