Spatial Proximity in Single Atomic Co Sites Boosts Water-Derived Active Hydrogen for Efficient Neutral...

Single-atom catalysts (SACs) are promising for nitrate reduction reaction (NO₃RR) to ammonia (NH₃), given their high atomic efficiency and tunable, well-defined structures. Yet, interactions between proximate atomic sites in NO₃RR are poorly understood. Here, we demonstrate the spatial proximity effect over N, P coordinated Co single atomic centers to boost NO₃RR catalytic activity. The adjacent configuration with CoN₄-P-CoN₄ atomic structures of the closest inter-site distance of ∼4.5 Å balance the water dissociation and NO₃RR via a dual-driven cascade mechanism in a neutral electrolyte. P site located at the shared second coordination shell dissociates water molecules to supply ample *H for the following hydrogenation process, while Co single site with optimized electronic state adsorbs and converts NO₃ ^- to NH₃. This study underscores the critical role of spatial proximity in SACs for NO₃RR, and may extend to diverse electrochemical transformations.