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

Abstract

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 hours, which is the longest catalytic durations ever reported. This work paves a novel approach for the design and synthesis of efficient NO3‐RR electrocatalysts.

Facet-Dependent Evolution of Active Components on Spinel Co3O4 for Electrochemical Ammonia Synthesis

“…This was evidenced by the smallest charge transfer resistance (R ct = 12.2 Ω at 0 V vs RHE) measured for the {111} facet catalyst, highlighting its kinetic advantage during the eNO 3 RR (Figure S11, Supporting Information). 20,67 To further confirm that the detected ammonia was produced by eNO 3 RR instead of environmental contamination or other factors, 14 N-and 15 N-isotopic labeling experiments were conducted and the 1 H nuclear magnetic resonance (NMR) spectra of the reacted electrolytes were measured (Figure 2d). The 1 H NMR spectra exhibited characteristic splitting patterns matching those of standard 14 NH 4 + and 15 NH 4 + for the respective isotopic reactants.…”