Efficient conversion of low-concentration nitrate sources into ammonia on a Ru-dispersed Cu nanowire electrocatalyst

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Engineering

Background:

• Nitrate ions in industrial wastewater and groundwater pose environmental challenges.
• Current electrochemical nitrate reduction methods suffer from low catalytic activity, especially at low concentrations.
• Sustainable ammonia generation from wastewater is a significant goal.

Purpose of the Study:

• To develop a high-performance catalyst for electrochemical nitrate reduction.
• To achieve efficient wastewater treatment and valuable ammonia synthesis.
• To investigate the catalytic mechanism using computational methods.

Main Methods:

• Fabrication of ruthenium-dispersed copper (Ru-Cu) nanowire catalysts.
• Electrochemical testing of nitrate reduction performance (current density, Faradaic efficiency).
• Wastewater treatment simulation from high (2,000 ppm) to low (<50 ppm) nitrate levels.
• Product separation and purification using air stripping.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism.

Main Results:

• The Ru-Cu nanowire catalyst achieved an industrial-relevant nitrate reduction current density of 1 A cm^-2.
• High ammonia (NH₃) Faradaic efficiency of 93% was maintained.
• Over 99% nitrate conversion was demonstrated, reducing concentration from 2,000 ppm to <50 ppm.
• High purity solid ammonium chloride (NH₄Cl) and liquid ammonia (NH₃) were successfully produced.
• DFT calculations indicated Ru sites are active for nitrate reduction and Cu sites suppress hydrogen evolution.

Conclusions:

• Ruthenium-dispersed copper nanowires represent a highly effective catalyst for electrochemical nitrate reduction.
• This technology offers a sustainable pathway for treating nitrate-contaminated water and producing valuable ammonia products.
• The catalyst's performance and the integrated process suggest practical applicability for industrial wastewater treatment.