Engineering Nitrogen Vacancy in Polymeric Carbon Nitride for Nitrate Electroreduction to Ammonia

Area of Science:

• Electrochemistry
• Materials Science
• Green Chemistry

Background:

• Electrocatalytic nitrate reduction to ammonia is crucial for energy conservation and environmental protection.
• Developing abundant, metal-free electrocatalysts with high performance remains a significant challenge.

Purpose of the Study:

• To synthesize and characterize polymeric graphitic carbon nitride (g-C3N4) with controlled nitrogen vacancies for electrocatalytic nitrate reduction.
• To investigate the role of nitrogen vacancies in enhancing the activity, selectivity, and stability of the electrocatalyst.

Main Methods:

• Electrochemical synthesis and characterization of g-C3N4 with varying nitrogen vacancies.
• Nitrate-to-ammonia conversion experiments using 15N isotope labeling.
• Ex situ and in situ characterization techniques.
• Density functional theory (DFT) calculations.

Main Results:

• The optimized g-C3N4 exhibited high Faradaic efficiency (89.96%) and selectivity (69.78%) for ammonia production.
• Stable electrocatalytic performance was observed over extended periods.
• 15N isotope labeling confirmed ammonia originated from nitrate reduction.
• DFT calculations revealed nitrogen vacancies promote nitrate adsorption and activation.

Conclusions:

• Polymeric graphitic carbon nitride with engineered nitrogen vacancies is a highly effective metal-free electrocatalyst for nitrate-to-ammonia conversion.
• Nitrogen vacancies are key to enhancing catalytic performance by optimizing intermediate adsorption and activation.
• This work provides a pathway for developing sustainable catalysts for nitrogen conversion.