Boosting Electrochemical Nitrate Reduction Over a Wide Concentration Range through Constructing Bidirectional...

Area of Science:

• Electrochemistry
• Materials Science
• Green Chemistry

Background:

• Electrocatalytic nitrate reduction reaction (NO₃RR) to ammonia (NH₃) offers sustainable nitrogen cycling and green NH₃ synthesis.
• Challenges in NO₃RR include mass transfer limitations at low nitrate concentrations and insufficient hydrogen supply at high concentrations.

Purpose of the Study:

• To design and evaluate a novel three-layer composite catalyst (Co/Cu/NC) for efficient NO₃RR over a broad concentration range.
• To understand the catalytic mechanism, particularly the role of bidirectional electron transport in enhancing performance.

Main Methods:

• Fabrication of Co@Cu core-shell nanoparticles embedded in N-doped carbon substrates (Co@Cu_x/NC).
• Electrocatalytic performance testing of the Co@Cu_1.0/NC catalyst across a wide range of nitrate concentrations (1–2000 mM).
• Experimental and theoretical studies (e.g., DFT) to elucidate the reaction mechanism and active sites.

Main Results:

• The optimal Co@Cu_1.0/NC catalyst demonstrated remarkable ammonia yield and Faradaic efficiency (FE_NH3) over a wide potential window and nitrate concentration range.
• Bidirectional electron transport between electron-deficient Cu sites (favoring nitrate adsorption and conversion to *NO₂) and electron-rich Co sites (facilitating H₂O dissociation to *H) was confirmed.
• The catalyst effectively addresses challenges posed by varying nitrate concentrations, from textile effluents to nuclear waste.

Conclusions:

• The designed Co/Cu/NC catalyst provides a highly effective solution for NO₃RR across an unprecedented range of nitrate concentrations.
• The bidirectional electron transport mechanism offers a novel strategy for designing advanced electrocatalysts for NO₃RR.
• This work paves the way for practical applications in green ammonia synthesis and wastewater treatment.