Synergistic Regulation of * NO Coupling and * H Supply on Sulfur‐Doped Zero‐Valent Iron Aerogels Drives Efficient Electroreduction of Nitrate to N ₂

Electrochemical nitrate (NO 3 − ) reduction to dinitrogen (N 2 ) is a promising approach for environmental remediation but suffers from the sluggish * NO coupling and excessive * H supply on traditional electrocatalysts. Herein, we construct a sulfur‐doped zero‐valent iron (Fe 0 @S) aerogel that enables highly selective electrochemical nitrate‐to‐dinitrogen conversion via * NO→ * N 2 O→N 2 path by synchronously regulating * H supply and * NO coupling. Mechanistic studies reveal that the aerogel's 3D porous framework enriches local NO 3 − near active sites, while strategic sulfur incorporation can weaken H 2 O adsorption and tune * NO 3 − binding strength, thereby lowering the energy barrier for * NO coupling into * N 2 O and subsequent reduction to N 2 . With a flow‐through electrolyzer, we achieve near‐complete removal of 50 mg/L NO 3 − from real surface and ground water with a high N 2 selectivity above 90%. This work provides a practical NO 3 − remediation method based on non‐noble metals and presents a simple strategy for the design of catalyst structure to improve N 2 selectivity.