Intermittent pulsed electrocatalysis adjusting Cu valence states for effective nitrite reduction to ammonia
Zhe Meng, Jian‐Hui Yi, Yutian Zhang, X. F. Sun, Xiaolei Huang, Miaomiao Shi, Feifei Zhang, Jun‐Min Yan, Qing Jiang
Abstract
Electrochemical nitrite (NO<sub>2</sub><sup>−</sup>) reduction offers a sustainable route for ammonia (NH<sub>3</sub>) 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 NO<sub>2</sub><sup>−</sup> concentrations. Herein, we report an intermittent pulsed electrolysis (IPE) strategy using copper oxide (Cu<sub><i>x</i></sub>O) nanowires, which significantly enhances the NH<sub>3</sub> yield rate and Faradaic efficiency (FE) at lower reactant concentrations. <i>In situ</i> experiments and theoretical calculations reveal that alternating between open-circuit and cathodic potentials modulates the copper oxidation states, stabilizing the catalytically active cuprous oxide (Cu<sub>2</sub>O). Consequently, the IPE approach provides an outstanding NH<sub>3</sub> yield rate of 115.10 mg·h<sup>−1</sup>·cm<sup>−2</sup> and FE of 91.14% in the presence of 25 mM NO<sub>2</sub><sup>−</sup>, markedly outperforming conventional constant potential electrolysis.