Electrochemical converting NO₂⁻ into NH₃ (NO₂RR) holds an enormous prospect to attain efficient NH₃ electrosynthesis and polluted NO₂⁻ mitigation. Herein, we report single-atom Co alloyed Ru (Co₁Ru) as an efficient and durable NO₂RR catalyst. Extensive experimental and theoretical investigations reveal that single-atom Co alloying of Ru enables the construction of Co₁-Ru heteronuclear active sites to synergistically promote NO₂⁻ activation/hydrogenation while suppressing the competitive H₂ evolution, rendering the greatly enhanced activity and selectivity of Co₁Ru towards the NO₂RR. Consequently, Co₁Ru assembled within a flow cell exhibits an impressive NH₃ yield rate of 2379.2 μmol·h⁻¹·cm⁻² with an NH₃-Faradaic efficiency of 92% at a high current density of 415.9 mA·cm⁻², which is among the highest NO₂RR performances reported to date.

Atomically dispersed Ir confined in amorphous MoO₃ (Ir₁/a-MoO₃) was designed as a high-efficiency catalyst for electrochemical reduction reaction of NO to NH₃ (NORR). Atomic precise characterizations reveal that isolated Ir atoms are immobilized in O-vacancies of amorphous MoO₃ to form Ir₁-O₅ moieties. Theoretical computations demonstrate that single-site Ir₁-O₅ can not only powerfully activate and hydrogenate NO with a near-zero energy barrier, but also exhibit a higher affinity to NO over H adatoms to suppress the competing hydrogen evolution and promote both NORR activity and selectivity. Consequently, Ir₁/a-MoO₃ shows the maximum NH₃ yield rate of 438.8 μmol∙h⁻¹∙cm⁻² and NH₃-Faradaic efficiency of 93.2%, representing one of the most efficient NORR catalysts to date.

Electrochemical NO reduction reaction (NORR) to generate NH₃ emerges as a fascinating approach to achieve both NO pollution mitigation and sustainable NH₃ synthesis. Herein, we demonstrate that single-atomic Cu anchored on MoS₂ (Cu₁/MoS₂) comprising Cu₁-S₃ motifs can serve as a highly efficient NORR catalyst. Cu₁/MoS₂ exhibits an NH₃ yield rate of 337.5 μmol·h⁻¹·cm⁻² with a Faradaic efficiency of 90.6% at −0.6 V vs. reversible hydrogen electrode (RHE). Combined experiments and theoretical calculations reveal that Cu₁-S₃ motifs enable the effective activation and hydrogenation of NO through a mixed pathway and simultaneously retard proton coverage, contributing to the high activity and selectivity of Cu₁/MoS₂ for the NORR.