ABSTRACT Electrochemical nitrate reduction to ammonia (NO 3 RR) represents a promising strategy for sustainable NH 3 synthesis and environmental remediation. However, it is critically challenged by high overpotentials and the hydrogen evolution reaction, especially in dilute nitrate environments. Herein, we report an atomically precise tandem electrocatalyst with fluorine and phosphorus dual‐doped cobalt (F, P‐Co) that achieves a record‐high NH 3 yield rate of 357.5 µmol h −1 cm −2 with 96.0% Faradaic efficiency at a low potential of –0.5 V vs. RHE. It exhibits exceptional stability for over 200 h in a 10 m m NO 3 − solution, ranking it among the best‐performing catalysts for low‐concentration NO 3 RR. Notably, in a biomass‐coupled flow cell, it attains a high current density of 200 mA cm −2 , demonstrating great promise for practical application. Mechanistic studies unveil that the F and P co‐doping synergistically alters the potential‐determining step and lowers the reaction barrier via an atomic relay mechanism involving * NO 2 spillover. Specifically, F‐Co sites facilitate the adsorption and reduction of NO 3 − to * NO 2 , whereupon the generated * NO 2 intermediate spontaneously migrates to adjacent P‐Co sites for subsequent hydrogenation. This work provides a fundamental principle for designing efficient tandem catalysts and establishes a viable pathway for energy‐efficient ammonia electrosynthesis.
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