Mo single-atom catalyst boosts nitrite electroreduction for ammonia synthesis

Electrocatalytic nitrite reduction to ammonia (NO2RR) presents an efficient approach for both wastewater treatment and powerful ammonia electrosynthesis. However, the activity and selectivity of NO2RR are limited by its complex six−electron transfer process and competitive hydrogen evolution. Herein, Mo single atoms anchored on a zirconium dioxide substrate (Mo1–ZrO2) are first explored as a highly selective and active catalyst for the NO2RR, exhibiting a maximum NH3−Faraday efficiency of 94.83% with a corresponding ammonia yield rate of 346.92 μmol h−1 cm−2 at −0.7 V vs. RHE. Theoretical calculations reveal that the isolated Mo sites can effectively activate nitrite, enhance nitrite−to−ammonia protonation energetics and prohibit competitive hydrogen evolution, thus leading to the remarkably enhanced selectivity and activity of Mo1–ZrO2 for the NO2RR.