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

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.