Boosting nitrate electroreduction to ammonia on atomic Ru-Co pair sites in hollow spinels

Electrocatalytic nitrate reduction reaction (NO3RR) to ammonia (NH3) provides a promising way to simultaneously remove widespread nitrogen pollution and electrify NH3 manufacturing. However, developing suitable electrocatalysts to efficiently convert NO3--to-NH3 remains a great challenge because of the slow kinetics of NO3RR and competitive hydrogen evolution reaction (HER). Herein, we reported a novel method to incorporating Ru single atom into hollow Co3O4 to construct atomically dispersed Ru-Co pair sites (Ru1-Co/HCO) for efficient NO3- electroreduction to NH3, with a maximal NH3 Faradaic efficiency of ∼100 % and a yield rate as high as 7.02 mg h−1 cm−2 (11.0 mg h−1 mgcat−1). The NO3RR activity can be explained by the synergistic tandem effect of Ru1-Co pair sites, where Ru sites are responsible for activating NO3- and stabilizing the intermediates, and neighboring Co site promotes water dissociation to generate active hydrogen (*H) for accelerating intermediate hydrogenation on Ru sites, alleviating the site competition between NO3RR and HER. A Zn–NO3- battery coupled with in-situ NH3 recovery device was also assembled to achieve the co-generation of high-purity NH4Cl fertilizer and electricity. Our work paves a new way for boosting NO3RR activity via constructing dual active sites.