A Reaction-Diffusion-Coupled Strategy for Ampere-Level Electrocatalytic Nitrate Reduction to Ammonia

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic nitrate reduction to ammonia (eNRA) presents a sustainable alternative to the Haber-Bosch process.
• Current eNRA methods face challenges with energy efficiency due to reaction-diffusion limitations.

Purpose of the Study:

• To develop a strategy that overcomes reaction-diffusion limitations in eNRA.
• To enhance the energy efficiency of ampere-level eNRA.
• To create a novel catalyst for efficient ammonia synthesis.

Main Methods:

• A reaction-diffusion-coupled strategy was implemented using a CuCoNiRuPt high-entropy alloy aerogel (HEAA).
• The HEAA catalyst was designed to homogenize energy barriers and accelerate mass transport.
• Performance was evaluated through ammonia yield rate, Faradaic efficiency, and overpotential measurements.

Main Results:

• The HEAA catalyst achieved an ammonia yield rate of 3.4 ± 0.3 mmol·h^-1·cm^-2.
• A high Faradaic efficiency of 98 ± 2% was recorded at a low overpotential of -0.05 V vs RHE.
• An energy efficiency of 41.5 ± 0.8% was realized, alongside durable operation at industrial current densities.
• A membrane electrode assembly electrolyzer demonstrated practical-scale ammonia production with a yield rate of 4.3 ± 0.1 mmol·h^-1·cm^-2 at 1 A·cm^-2.

Conclusions:

• The developed reaction-diffusion-coupled strategy and HEAA catalyst significantly improve the energy efficiency of eNRA.
• This work paves the way for industrial-scale, carbon-neutral ammonia production via electrocatalysis.
• The findings offer new avenues for designing efficient catalysts for sustainable chemical synthesis.