Iridium single-atom catalyst for highly efficient NO electroreduction to NH₃

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.