Cu-Co Dual Sites Tandem Synergistic Effect Boosting Neutral Low Concentration Nitrate Electroreduction to Ammonia

Electrochemical nitrate reduction reaction (NO₃ ^-RR) has emerged as an alternative strategy for wastewater treatment and ammonia production in neutral low-concentration nitrate. However, the electrocatalyst faces the challenge of limited NO₃ ^- distribution and deficient active hydrogen (H_ads) on the catalyst surface resulting from the low concentration of NO₃ ^- and the difficulty of water splitting under neutral conditions. Here, a Cu-Co dual sites tandem synergistic catalysis mechanism has been proposed by doping Cu into CoP to facilitate the adsorption and conversion of NO₃ ^- on Cu and to accelerate the water splitting on CoP leading to the significantly high NO₃ ^-RR performance. The designed Cu-CoP catalyst exhibits an ammonia yield of 7.65 mg h^-1 cm^-2 and a Faraday efficiency of 85.1% at -1.0 V under neutral low-concentration nitrate (10 m M), which is the highest ammonia yield in the reported data. In situ characterization and theoretical calculations confirm the tandem synergistic effect, in which the Cu site favors the adsorption and activation of NO₃ ^- to form NO₂ ^-, and concurrently modulates the electronic structure of the Co site with optimized H_ads adsorption resulting in the significantly enhanced NO₃ ^-RR at neutral low concentration nitrate.