Boosting Electrochemical Nitrate Reduction at Low Concentrations Through Simultaneous Electronic States Regulation and Proton Provision

Abstract Electrochemically converting nitrate (NO 3 − ) into ammonia (NH 3 ) has emerged as an alternative strategy for NH 3 production and effluent treatment. Nevertheless, the electroreduction of dilute NO 3 − is still challenging due to the competitive adsorption between various aqueous species and NO 3 − , and unfavorable water dissociation providing * H. Herein, a new tandem strategy is proposed to boost the electrochemical nitrate reduction reaction (NO 3 RR) performance of Cu nanoparticles supported on single Fe atoms dispersed N‐doped carbon (Cu@Fe 1 ‐NC) at dilute NO 3 − concentrations (≤100 ppm NO 3 − ‐N). The optimized Cu@Fe 1 ‐NC presents a FE NH3 of 97.7% at −0.4 V versus RHE, and a significant NH 3 yield of 1953.9 mmol h −1 g Cu −1 at 100 ppm NO 3 − ‐N, a record‐high activity for dilute NO 3 RR. The metal/carbon heterojunctions in Cu@Fe 1 ‐NC enable a spontaneous electron transfer from Cu to carbon substrate, resulting in electron‐deficient Cu. As a result, the electron‐deficient Cu facilitates the adsorption of NO 3 − compared with the pristine Cu. The adjacent atomic Fe sites efficiently promote water dissociation, providing abundant * H for the hydrogenation of * NO x e at Cu sites. The synergistic effects between Cu and single Fe atom sites simultaneously decrease the energy barrier for NO 3 − adsorption and hydrogenation, thereby enhancing the overall activity of NO 3 − reduction.