Atomically precise alkynyl-protected Ag ₁₉ Cu ₂ nanoclusters: synthesis, structure analysis, and electrocatalytic CO ₂ reduction application

We report the synthesis, structure analysis, and electrocatalytic CO₂ reduction application of Ag₁₉Cu₂(CCAr^F)₁₂(PPh₃)₆Cl₆ (abbreviated as Ag₁₉Cu₂, CCAr^F: 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters. Ag₁₉Cu₂ has characteristic absorbance features and is a superatomic cluster with 2 free valence electrons. Single-crystal X-ray diffraction (SC-XRD) revealed that the metal core of Ag₁₉Cu₂ is composed of an Ag₁₁Cu₂ icosahedron connected by two Ag₄ tetrahedra at the two terminals of the Cu-Ag-Cu axis. Notably, Ag₁₉Cu₂ exhibited excellent catalytic performance in the electrochemical CO₂ reduction reaction (eCO₂RR), manifested by a high CO faradaic efficiency of 95.26% and a large CO current density of 257.2 mA cm^-2 at -1.3 V. In addition. Ag₁₉Cu₂ showed robust long-term stability, with no significant drop in current density and FE_CO after 14 h of continuous operation. Density functional theory (DFT) calculations disclosed that the high selectivity of Ag₁₉Cu₂ for CO in the eCO₂RR process is due to the shedding of the -CCAr^F ligand from the Ag atom at the very center of the Ag₄ unit, exposing the active site. This study enriches the potpourri of alkynyl-protected bimetallic nanoclusters and also highlights the great advantages of using atomically precise metal nanoclusters to probe the atomic-level structure-performance relationship in the catalytic field.