H* Species Regulation by Mn‐Co(OH)2 for Efficient Nitrate Electro‐reduction in Neutral Solution

Abstract During the electrocatalytic NO 3 − reduction reaction (NO 3 − RR) under neutral condition, the activation of H 2 O to generate H* and the inhibition of inter‐H* species binding, are critically important but remain challenging for suppressing the non‐desirable hydrogen evolution reaction (HER). Here, a Mn‐doped Co(OH) 2 (named as Mn‐Co(OH) 2 ) has been synthesized by in situ reconstruction in the electrolyte, which is able to dissociate H 2 O molecules but inhibits the binding of H* species between each other owing to the increased interatomic spacing by the Mn‐doping. The Mn‐Co(OH) 2 electrocatalyst offers a faradaic efficiency (FE) of as high as 98.9±1.7% at −0.6 V vs. the reversible hydrogen electrode (RHE) and an energy efficiency (EE) of 49.90±1.03% for NH 3 production by NO 3 − RR, which are among the highest of the recently reported state‐of‐the‐art catalysts in neutral electrolyte. Moreover, negligible degradation at −200 mA cm −2 has been found for at least 500 h, which is the longest catalytic durations ever reported. This work paves a novel approach for the design and synthesis of efficient NO 3 − RR electrocatalysts.