Intermittent pulsed electrocatalysis adjusting Cu valence states for effective nitrite reduction to ammonia

Electrochemical nitrite (NO₂⁻) reduction offers a sustainable route for ammonia (NH₃) synthesis while simultaneously removing contaminants in wastewater. However, its efficiency is often limited by low catalytic efficiency and the competitive hydrogen evolution reaction at low NO₂⁻ concentrations. Herein, we report an intermittent pulsed electrolysis (IPE) strategy using copper oxide (Cu_xO) nanowires, which significantly enhances the NH₃ yield rate and Faradaic efficiency (FE) at lower reactant concentrations. In situ experiments and theoretical calculations reveal that alternating between open-circuit and cathodic potentials modulates the copper oxidation states, stabilizing the catalytically active cuprous oxide (Cu₂O). Consequently, the IPE approach provides an outstanding NH₃ yield rate of 115.10 mg·h⁻¹·cm⁻² and FE of 91.14% in the presence of 25 mM NO₂⁻, markedly outperforming conventional constant potential electrolysis.