In Situ Dynamic Reconstruction Asymmetric P─Co─O/OH Sites for Sustainable Gram-Level Electrocatalytic Ammonia...

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Chemistry

Background:

• Electrochemical conversion of nitrite/nitrate to ammonia offers a sustainable route for ammonia production.
• Challenges remain in balancing catalyst activity and stability for gram-level ammonia production.

Purpose of the Study:

• To develop a highly active and stable electrode for efficient ammonia synthesis via nitrite reduction.
• To establish a complete system for direct air-to-ammonia conversion using integrated electrocatalysis, plasma, and solar power.

Main Methods:

• Fabrication of a low-crystallinity phosphorus-doped cobalt electrode (P─Co/NF).
• Electrochemical characterization and theoretical calculations to understand catalytic mechanisms.
• Integration of the electrode with microwave plasma and intermittent solar power for a complete system.

Main Results:

• Achieved an ammonia yield rate of 414.51 mg h⁻¹ cm⁻² and 1000 h stability.
• Identified a dynamically evolved P─Co/Co(OH)₂ heterostructure with asymmetric active sites optimizing NO₂⁻ activation and water dissociation.
• Demonstrated a direct air-to-ammonia conversion system yielding 1.19 g per day with >90% Faradaic efficiency.
• Scaled up to a 100 cm² flow cell, achieving an ammonia production rate of 4.97 g h⁻¹.

Conclusions:

• The P─Co/NF electrode and the integrated system overcome the activity-stability tradeoff for industrial-level ammonia production.
• The study provides a paradigm for designing dynamic asymmetric active sites for sustainable ammonia synthesis.
• Paves the way for decentralized and sustainable ammonia production using renewable energy.