Electrocatalytic N₂-to-NH₃ conversion with high faradaic efficiency enabled using a Bi nanosheet array.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic nitrogen (N2) reduction to ammonia (NH3) is a sustainable alternative to the Haber-Bosch process.
• Competitive hydrogen evolution reaction (HER) significantly limits NH3 production efficiency.

Purpose of the Study:

• To investigate metallic bismuth (Bi) nanosheet arrays as a novel catalyst for electrocatalytic N2 reduction.
• To evaluate the catalytic performance and mechanism of Bi-based catalysts in acidic media.

Main Methods:

• Fabrication of a 3D catalyst electrode using a Bi nanosheet array on Cu foil.
• Electrochemical characterization including N2 reduction and HER measurements.
• Density functional theory (DFT) calculations to elucidate the reaction mechanism.

Main Results:

• The Bi nanosheet array achieved a high Faradaic efficiency of 10.26% for NH3 formation at -0.50 V vs. RHE.
• A high NH3 yield rate of 6.89 × 10^-11 mol s^-1 cm^-2 was obtained.
• DFT calculations indicated that Bi effectively activates the N≡N bond and favors the alternating mechanism.

Conclusions:

• Metallic Bi nanosheets demonstrate superior catalytic activity for N2 reduction electrocatalysis in acidic media.
• Bi-based catalysts offer a promising noble-metal-free alternative for efficient and sustainable ammonia synthesis.
• The study provides mechanistic insights into Bi-catalyzed N2 fixation, paving the way for further catalyst development.