Structure‐Property Engineering in Ag 23 Nanoclusters for Electrocatalytic Nitrate Reduction

Electrocatalytic nitrate reduction reaction (NO 3 RR) provides a sustainable pathway for ambient ammonia synthesis; however, achieving concurrent high activity, high selectivity and appropriate stability of catalysts remains a substantial challenge. Here we report the synthesis and structure‐property engineering of a class of atomically precise silver nanoclusters via geometric tuning and copper substitution. Compared with the parent nanocluster Ag 23 (PET) 18 (PPh 3 ) 8 (abbreviated as Ag 23 ‐1), a Cu‐substituted Ag 19 Cu 4 (SCH 2 PhCl) 18 (PPh 3 ) 4 nanocluster (i.e., Ag 19 Cu 4 ) modulates the electronic structure and catalytic active sites, giving rise to an improved Faradaic efficiency (FE ∼71%) upon NO 3 RR electrocatalysis but with irreversible alteration of the metal oxidation states. Intriguingly, a geometry‐tuned [Ag 23 (SAdm) 12 ] 3+ cluster (Ag 23 ‐2) exhibits enhanced stability due to its superatomic eight‐electron shell structure (1S 2 |1P 6 ||) and delivers an NH 3 yield of ∼6.5 mg NH3 ·h −1 ·mg −1 cat at −0.9 V, outperforming the parent Ag 23 ‐1 and comparable with the Ag 19 Cu 4 NCs. Density functional theory (DFT) calculations indicate that the reaction proceeds via a stepwise hydrogenation pathway, with the *NO 2 ‐to‐*NO conversion serving as the rate‐determining step, where the energy barriers can be efficiently lowered by the Ag 19 Cu 4 NCs. This work illustrates that structural engineering constitutes an effective strategy for tailoring activity, selectivity, and stability in atomically precise nanocluster catalysts.