Embedded Fe-Cu Pairs Enable Tandem Nitrate-to-Ammonia Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Chemistry

Background:

• Electrochemical nitrate reduction (e-NO3RR) to ammonia (NH3) offers integrated environmental remediation and resource regeneration.
• Challenges include competing Hydrogen Evolution Reaction (HER) at neutral pH, limiting efficiency and selectivity.
• Sustainable nitrogen cycling and circular economy principles are key drivers.

Purpose of the Study:

• To design a novel electrocatalyst for efficient and selective electrochemical nitrate reduction to ammonia.
• To overcome limitations of conventional bimetallic catalysts in neutral media.
• To elucidate the mechanism of enhanced catalytic activity.

Main Methods:

• Design and synthesis of a Fe-Cu pair electrocatalyst (Cu-N3/Fe3-N8).
• Electrochemical characterization including cyclic voltammetry and chronoamperometry.
• Analysis of ammonia production rate and Faradaic efficiency.

Main Results:

• The Fe-Cu electrocatalyst achieved an NH3 production rate of 18.83 mg·h−1·mgcat−1 at -0.65 V vs RHE.
• A high Faradaic efficiency of 97.1% for NH3 was observed.
• The catalyst demonstrated enhanced nitrate adsorption and facilitated nitrite adsorption/water activation via a charge gradient relay mechanism.

Conclusions:

• The designed Fe-Cu electrocatalyst significantly enhances e-NO3RR efficiency and selectivity under neutral pH.
• A spatially separated charge gradient mechanism optimizes multi-step reaction intermediates.
• This work provides insights for designing multi-active-site electrocatalysts for nitrogen resource conversion.