Electroreduction of Nitrite to Ammonia over a Cobalt Single-Atom Catalyst

Electrochemical nitrite-to-ammonia reduction (NO2RR) holds great promise for converting harmful NO2– into valuable NH3. Herein, we develop Co single atoms dispersed on a C3N4 substrate (Co1/C3N4) as an efficient catalyst toward the NO2RR. Experimental and theoretical investigations reveal that single-atom Co sites can effectively active NO2– and optimize the formation energy of the key *NOH intermediate to promote the NO2– → NH3 energetics. Remarkably, Co1/C3N4 equipped in a flow cell delivers the exceptional NH3–Faradaic efficiency of 97.9% and NH3 yield rate of 1080.3 μmol h–1cm–2 at an industrial-level current density of 355 mA cm–2, along with a long-term durability of 100 h of electrolysis, showing the considerable potential for practical NH3 electrosynthesis.