Gram-level NH₃ Electrosynthesis via NO_x reduction on a Cu Activated Co Electrode

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• The Haber-Bosch process, while crucial for ammonia production, is highly energy-intensive.
• Ambient electrochemical ammonia synthesis presents a sustainable alternative but faces challenges in achieving industrial-scale current densities and yields.
• Nitrite reduction is an emerging pathway for electrochemical ammonia synthesis.

Purpose of the Study:

• To develop a high-rate ammonia synthesis method via nitrite reduction.
• To investigate the performance of a copper-activated cobalt electrode in a bipolar membrane electrolyzer.
• To demonstrate the large-scale feasibility of this novel ammonia production technique.

Main Methods:

• Utilizing a bipolar membrane (BPM) electrolyzer with a Cu-activated Co foam electrode for nitrite reduction.
• Employing an alkaline electrolyte in an H-type cell configuration.
• Conducting in situ experiments and theoretical calculations to understand reaction mechanisms.

Main Results:

• Achieved a high current density of 2.64 A cm⁻² with 96.45% Faradaic efficiency for ammonia production.
• Obtained a high ammonia yield rate of 279.44 mg h⁻¹ cm⁻².
• Demonstrated a large-scale ammonia production of 4.11 g h⁻¹ using a homemade reactor.

Conclusions:

• The Cu-activated Co electrode significantly enhances the rate and efficiency of ammonia synthesis via nitrite reduction.
• The bipolar membrane electrolyzer design is effective in maintaining ion balance and electrolyte levels for sustained operation.
• This approach shows strong potential for practical, large-scale, and sustainable ammonia production.