Main-Group Sn Single Atoms on MoS2–x for Selective Nitrite Electroreduction to Ammonia

Electrocatalytic NO₂^--to-NH₃ reduction (NO₂RR) offers an attractive way to remedy polluted NO₂^- and produce value-added NH₃. In this study, main-group Sn single atoms anchored on S-vacancy-rich MoS_2-x (Sn₁/MoS_2-x) are explored as a highly selective NO₂RR catalyst. Combined theoretical computations and in situ spectroscopic measurements reveal that the isolated Sn₁ sites of Sn₁/MoS_2-x can not only promote NO₂^--to-NH₃ activation and hydrogenation but also favor NH₃ desorption and restrict H adsorption, thus enabling a highly selective NO₂RR for NH₃ synthesis. Remarkably, Sn₁/MoS_2-x exhibits an NH₃-Faradaic efficiency of 98.8% and an NH₃ yield rate of 1922.3 μmol h^-1 cm^-2 in a flow cell, outperforming most of the NO₂RR catalysts reported to date.