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.