Tandem Catalysis Enables High‐Rate Nitrate Electroreduction via Interfacial Water Regulation

ABSTRACT The electrocatalytic nitrate reduction (NO 3 RR) for rapid nitrate removal offers a sustainable wastewater treatment pathway, but suffers from low activity for practical applications. Herein, we synthesize a tandem catalyst with silver (Ag) nanoparticles implanted in iron phosphide (FeP) nanosheets, demonstrating a remarkable nitrate removal rate of 16.67 mg N L −1 h −1 (98% NO 3 − ‐N conversion and 99% N 2 selectivity via a coupled electro‐chemical pathway) and up to 40 cycles of electrocatalytic stability (6 h per cycle). Mechanistic study by a series of in situ experiments reveals a decoupling and tandem catalytic mechanism for achieving high‐rate activity: the favorable nitrate reduction to nitrite on Ag nanoparticles, and the subsequent accelerated interfacial water activation with elevated local * H concentration on FeP nanosheets. Leveraging this tandem catalyst design, we further develop a paired‐electrolysis flow‐cell reactor integrating NO 3 RR with sulfion oxidation. This system co‐valorizes both contaminants by oxidizing sulfion to elemental sulfur while reducing nitrate to N 2 , achieving an enhanced nitrogen removal rate of ∼ 31.7 mg N L −1 h −1 .