Boron and Nitrogen Bridged Mn Single‐Atom Catalyst for Highly Efficient Nitrogen Electroreduction to Ammonia

Ammonia (NH 3 ) is a globally important commodity for energy storage, carbon‐free energy carrier, and fertilizer production, but its synthesis through the Haber‐Bosch process is energy‐intensive and emits significant amounts of CO 2 . Electrochemical reduction of N 2 under ambient conditions is a green and potentially promising approach for NH 3 synthesis, but is limited by a high energy barrier of the first *N 2 protonation step, competitive hydrogen evolution reaction, and lack of efficient electrocatalysts. Herein, a newly designed electrocatalyst is reported by bridging B 2 N 2 with an Mn single atom in B/N co‐doped carbon (denoted MnB 2 N 2 /C), which exhibits a highly efficient N 2 reduction reaction (N 2 RR) activity with NH 3 Faradaic efficiency (FE NH3 ) of ≈37.15% in the aqueous phase system and good electrocatalytic and material stability. The FE NH3 of the MnB 2 N 2 /C catalyst is ≈2.1 times higher than that of the as‐synthesized MnN 4 /C counterpart under the same conditions. In the gas phase system, this MnB 2 N 2 /C catalyst shows a remarkably high NH 3 production rate (87.54 µg mg cat. −1 h −1 ) and FE NH3 (45.66%). The density functional theory (DFT) calculations revealed that the high N 2 RR to NH 3 performance arising from the Mn site and the neighboring B site suppresses the parasitic HER on the Mn sites.