Spatial Decoupling of Adsorption and Transformation Sites on Ag‐Cu Dual‐Single‐Atom Catalysts for Highly Selective Photocatalytic Nitrate‐to‐Ammonia Reduction

Abstract Photocatalytic nitrate (NO 3 – ) reduction to ammonia (NH 3 ) presents a sustainable solution for simultaneous NH 3 synthesis and wastewater remediation. However, achieving high selectivity is challenging, plagued by sluggish kinetics and parasitic side reactions. In this study, we rationally design a synergistic Ag‐Cu dual‐atom catalyst on g‐C 3 N 4 (AgCu‐CN) that embodies a spatially decoupled tandem scheme. We demonstrate that the oxophilic Cu 1 site serve as Lewis acid centers to efficiently capture and activate NO 3 – , before the crucial *NO intermediate is shuttled to adjacent Ag 1 site, which is intrinsically inert toward the hydrogen evolution reaction, act as dedicated hydrogenation center for rapid and deep *NO reduction. This atomic‐level synergy manifests in a state‐of‐the‐art performance, with AgCu‐CN delivering an impressive 98% NH 3 selectivity and a production rate of 630.5 µmol h −1 g −1 under visible light. In situ spectroscopic studies and theoretical calculations corroborate the tandem mechanism and the critical role of the Ag‐Cu dual sites in steering reaction selectivity. This study establishes a powerful tandem catalytic design principle to manage the selectivity challenges in complex multi‐proton/electron reactions.