Surface Structure Reformulation from CuO to Cu/Cu(OH)₂ for Highly Efficient Nitrate Reduction to Ammonia

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nitrate (NO3-) to ammonia (NH3) conversion offers a sustainable route for green ammonia production and nitrogen cycle remediation.
• Developing efficient electrocatalysts is crucial for advancing this electrochemical conversion process.

Purpose of the Study:

• To report an efficient catalyst for electrochemical nitrate reduction to ammonia.
• To investigate the structural and phase transformations influencing catalytic activity.
• To elucidate the synergistic mechanisms promoting ammonia synthesis.

Main Methods:

• Electrochemical synthesis of spherical CuO nanoparticles with oxygen vacancies.
• Electrocatalytic performance testing in neutral electrolyte.
• Structural and phase analysis using advanced characterization techniques.
• Density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• Achieved high NH3 yield (15.53 mg h-1 mgcat-1) and Faraday efficiency (90.69%) at -0.80 V vs. RHE.
• Observed structural transformation from spherical to layered network, increasing active sites.
• Identified phase transition from CuO to Cu/Cu(OH)2, enhancing NO3- adsorption and inhibiting hydrogen evolution.
• DFT confirmed the synergistic role of Cu(OH)2 and Cu(111) in promoting NH3 production.

Conclusions:

• The developed spherical CuO catalyst with oxygen vacancies exhibits excellent performance for electrochemical nitrate-to-ammonia conversion.
• Structural and phase changes, particularly the formation of Cu(OH)2 and Cu(111) surfaces, are key to the enhanced catalytic activity.
• This work provides a promising direction for designing Cu-based oxide electrocatalysts for green ammonia synthesis.