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

• Published in: Angewandte Chemie International Edition 2024-03, Vol.63 (11), p.e202400206-n/a
• Main Authors: Liang, Shaozhen, Teng, Xue, Xu, Heng, Chen, Lisong, Shi, Jianlin
• Format: Article
• Language: English
• Subjects: Ammonia; Binding; Catalysts; Chemical reduction; Electrocatalysts; Electrocatalytic nitrate reduction; Electrolytes; Energy efficiency; H regulation; Hydrogen evolution reactions; Mn-Co(OH)2 nanosheets; neutral nitrate condition; Nitrates
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202400206

During the electrocatalytic NO3− reduction reaction (NO3−RR) under neutral condition, the activation of H2O 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 H2O 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 NH3 production by NO3−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 NO3−RR electrocatalysts. The Mn doped Co(OH)2 electrocatalyst was designed to promote the NO3−RR to NH3 by accelerating the H* generation from water dissociation and inhibiting the H* binding between each other for hydrogen evolution, which ensures the much enhanced FE (98.9%) and stability (500 h) for ammonia production.