Structure identification and mechanism exploration of ultralow-content of metal doped Cu for efficient electrochemical production of ammonia in dilute nitrate concentrations

Abstract

To facilitate the dilute electrochemical nitrate reduction reaction (NO₃⁻RR), definite structure identification and clear mechanism exploration are essential and challenging for the development of efficient electrocatalysts. Herein, an ultralow-content of metal (M, including Fe, Co and Ni) was introduced into Cu (M–Cu) by in situ electrochemical reconstitution of the oxides for NO₃⁻RR at dilute NO₃⁻ concentration (≤100 ppm NO₃⁻–N). Electrochemical evaluation reveals that the introduction of low-content metal can simultaneously facilitate the activity and selectivity of NO₃⁻RR. For example, the Fe–Cu exhibits a significant FE of 93.4% and yield rate of 323.1 mmol h⁻¹ g_cat⁻¹ for NH₄⁺ formation, superior to those for Cu. Theoretical and experimental results show that the introduction of Fe simultaneously optimizes the adsorption of *NO₂ and *H, and thus facilitates the subsequent hydrogenation, beneficial for NO₃⁻RR. This study provides a universal metal doping strategy for boosting NO₃⁻RR by the adsorption-transfer mechanism of *H.