Single-atom Zn on MnO2 for selective nitrite electrolysis to ammonia

Electrochemical nitrite-to-ammonia reduction (NO2RR) represents an attractive method to simultaneously attain hazardous NO2− removal and renewable NH3 synthesis. In this study, we first design single-atom Zn anchored on MnO2 nanowires (Zn1/MnO2) as a highly active and durable NO2RR catalyst. Atomic-scale characterizations reveal that Zn single atoms are coordinated with three surface-O atoms of MnO2 to form Zn1-O3 units. A combination of in situ electrochemical measurements and theoretical computations unravel that Zn1-O3 units enhance the NO2− activation, stabilize the key intermediate of *NHO and lower the energy barrier of NO2−-to-NH3 hydrogenation process. Consequently, Zn1/MnO2 assembled in a special flow cell reactor achieves the highest NH3 yield rate of 1559.1 μmol h−1cm−2 and NH3-Faradaic efficiency of 95.3 % at −288.5 mA cm−2, superior to nearly all previously reported NO2RR electrocatalysts.