Atomically Dispersed Sn Confined in FeS₂ for Nitrate-to-Ammonia Electroreduction

Electrocatalytic NO3- reduction to NH3 (NO3RR) is an efficient strategy to simultaneously mitigate NO3- contamination and produce sustainable NH3. Herein, atomically dispersed Sn confined in FeS2 (Sn-FeS2) is reported as an effective and robust NO3RR catalyst, achieving a maximum NH3-Faradaic efficiency of 96.7% with a corresponding NH(3 )yield rate of 15.8 mg h(-1) cm(-2), along with an excellent catalytic stability. Atomic coordination characterizations of Sn-FeS2 unravel that single-atomic Sn bonds with the surrounding Fe atoms to construct the unique p-d hybridized Sn-Fe pair sites. Combining theoretical investigations and operando spectroscopic measurements unveil that Sn-Fe pair sites can synergistically promote the NO3- activation and N=O bond dissociation, accelerate the protonation energetics of NO3--to-NH3 pathway and suppress the competing hydrogen evolution, eventually drastically enhancing the NO3RR activity and selectivity.