Construction of Atomic-Scale Compressive Strain for Oxime Electrosynthesis

Tuning the surface strain is a powerful strategy to enhance the catalytic activity of metal nanocatalysts, yet an atomically precise catalyst with intramolecular strain to unlock the atomic-level strain-structure-activity relationship is still highly desired. Herein, we report the synthesis, structural anatomy, and catalytic performance toward cyclohexanone oxime electrosynthesis of an atomically precise Ag16Cu18(C≡C-C6H11)24 (Ag16Cu18) nanocluster, which has a Cu6 ring in the center. The Cu-Cu distance in the Cu6 ring is only 1.616 Å in a single crystal, the shortest Cu-Cu bond in Cu nanomaterials to date. Furthermore, once Ag16Cu18 was loaded onto carbon paper, the ultrashort Cu-Cu bond elongated to ∼2.40 Å, still showing strong intramolecular compressive strain. Ag16Cu18 exhibited excellent catalytic activity toward oxime electrosynthesis, manifested by a maximal Faradaic efficiency, yield, and yield rate of cyclohexanone oxime reaching 47.4%, 95.4%, and 2.66 mmol·h-1·cm-2 at -0.35 V, respectively. In-situ attenuated total reflection surface-enhanced infrared spectroscopy revealed that the Cu sites adjacent to the Ag atoms primarily reduce NO and stabilize it at the *NH2OH stage, while the Cu sites with compressive strain provide H* for NO reduction and adsorb cyclohexanone to react with *NH2OH, forming cyclohexanone oxime simultaneously. Density functional theory calculations confirmed the presence of compressive strain in the Cu6 ring, which facilitates H* formation and cyclohexanone adsorption, hence significantly contributing to oxime generation. This study not only reports a case of atomically precise clusters with intramolecular compressive strain but also provides an atomic-level understanding for employing bimetallic nanocluster-based catalysts toward the electrosynthesis of valuable organic molecules.