Carbon-Confined Fe₃C/Fe₃N Janus Interfaces for Selective Nitric Oxide-to-Ammonia Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic nitric oxide reduction to ammonia (NORR) is crucial for pollutant valorization and sustainable nitrogen conversion.
• Achieving high activity and selectivity in NORR requires precise control over NO transport, activation, and hydrogenation at the gas-liquid-solid interface.

Purpose of the Study:

• To develop a highly active and selective noble-metal-free catalyst for NORR.
• To investigate the mechanistic pathways governing efficient electroreduction of nitric oxide to ammonia.

Main Methods:

• Fabrication of a self-supported, earth-abundant Fe3C/Fe3N@C catalyst featuring defect-rich Janus nanostructures confined within graphitic carbon.
• Electrochemical evaluation of the catalyst's performance, including NH3 yield rate and Faradaic efficiency.
• Mechanistic studies employing spectroscopic and theoretical analyses to elucidate the roles of different catalytic sites and the carbon shell.

Main Results:

• The Fe3C/Fe3N@C catalyst achieved an NH3 yield rate of 468.3 µmol h-1 cm-2 with 94.2% Faradaic efficiency at -0.6 V vs RHE.
• The graphitic carbon shell enhanced NO diffusion by mitigating steric and dynamic constraints.
• Fe3C sites facilitated NO activation, while Fe3N sites promoted H2O dissociation for hydrogenation.

Conclusions:

• The developed catalyst represents one of the most efficient NORR electrocatalysts reported to date.
• Spatial coupling of mass-transfer promotion, NO activation, and interfacial hydrogen generation is key to efficient NORR.
• Carbon-confined carbide/nitride Janus interfaces offer a promising design strategy for high-performance NORR catalysts.