Modulating tenorite-based bimetallic electrocatalysts for highly selective ammonia oxidation to N₂

Area of Science:

• Electrochemistry
• Environmental Science
• Materials Science

Background:

• Electrochemical ammonia oxidation reaction (EAOR) is promising for treating low-concentration ammonia in wastewater.
• Achieving selective conversion of ammonia to non-toxic nitrogen (N2) is challenging in complex matrices.
• Copper (Cu) passivation hinders EAOR performance.

Purpose of the Study:

• To develop noble metal-plated copper electrodes (M-Cu) to mitigate Cu passivation and enhance EAOR.
• To investigate the catalytic performance and selectivity of M-Cu electrodes for ammonia oxidation.
• To elucidate the reaction mechanism and energy consumption of the optimized EAOR process.

Main Methods:

• Synthesis of M-Cu electrodes (M = Ru, Rh, Pd, Pt, Ag) by plating noble metals onto copper crystals.
• Electrochemical characterization including cyclic voltammetry and chronoamperometry.
• Mechanistic analysis using electrochemical techniques and kinetic modeling.

Main Results:

• Cu sublayer facilitated ammonia adsorption and dehydrogenation; surface noble metals improved stability and surface area.
• PtCu and AgCu electrodes achieved >80% N2 selectivity and near-complete ammonia removal at +1.0 V (vs. RHE) and pH 11.
• AgCu electrode exhibited the lowest energy consumption for ammonia oxidation.

Conclusions:

• M-Cu electrodes effectively enhance EAOR performance and mitigate copper passivation.
• The synergistic effect between OH- and M sites, mediated by the Cu2O/CuO redox couple, drives NHx dehydrogenation and N2 formation.
• Optimized M-Cu electrodes demonstrate potential for treating industrial wastewater containing ammonia.