Multisite (Cu⁰/Cu⁺/Cu²⁺-Fe) Interfaces Enhance Nitrate Adsorption and Active Hydrogen Utilization for Ammonia...

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Science

Background:

• Nitrate (NO$_{3}$$^{-}$) electroreduction to ammonia (NH$_{3}$) is crucial for environmental remediation and nitrogen recovery.
• Existing catalysts often show low ammonia yield rates and Faradaic efficiency (FE) in near-neutral, low-concentration nitrate environments.
• Development of efficient catalysts is needed to overcome these limitations for practical applications.

Purpose of the Study:

• To develop a novel catalyst for efficient electroreduction of nitrate to ammonia.
• To investigate the catalytic performance and mechanism of Fe-doped multivalent copper oxide (Cu$_{x}$O-Fe).
• To demonstrate the catalyst's applicability in real-world water samples.

Main Methods:

• Synthesis of Fe-doped multivalent copper oxide (Cu$_{x}$O-Fe) catalyst.
• Electrochemical evaluation of nitrate reduction reaction (NO$_{3}$RR) performance, including ammonia yield rate, FE, and selectivity.
• In situ characterizations and theoretical calculations to elucidate the reaction mechanism.
• Testing the catalyst in actual surface water and landfill leachate.

Main Results:

• The Cu$_{x}$O-Fe catalyst achieved a superior NH$_{3}$ yield rate of 3.5 mg·h$^{-1}$·mg$_{cat}$$^{-1}$ and an excellent FE of 97.7%.
• The catalyst exhibited high NH$_{3}$ selectivity (98.7%) in 50-200 ppm nitrate electrolytes, outperforming other catalysts.
• Fe doping optimized the electronic structure of Cu$_{x}$O, facilitating NO$_{3}$$^{-}$ adsorption, H$_{2}$O dissociation, and lowering energy barriers for NH$_{3}$ synthesis.
• The Cu$_{x}$O-Fe catalyst showed high performance in surface water (>94.3% NH$_{3}$ selectivity) and landfill leachate (92.6% selectivity).

Conclusions:

• Fe doping in multivalent copper oxide creates multisite interfaces that significantly enhance nitrate electroreduction to ammonia.
• The catalyst's distinct active sites for NO$_{3}$RR and H$_{2}$O dissociation enable efficient and non-competitive reaction pathways.
• The Cu$_{x}$O-Fe catalyst demonstrates strong potential for practical applications in environmental remediation and nitrogen recovery.