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 CO 2 reduction application of Ag 19 Cu 2 (CCAr F ) 12 (PPh 3 ) 6 Cl 6 (abbreviated as Ag 19 Cu 2 , CCAr F : 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters. Ag 19 Cu 2 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 Ag 19 Cu 2 is composed of an Ag 11 Cu 2 icosahedron connected by two Ag 4 tetrahedra at the two terminals of the Cu-Ag-Cu axis. Notably, Ag 19 Cu 2 exhibited excellent catalytic performance in the electrochemical CO 2 reduction reaction (eCO 2 RR), 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. Ag 19 Cu 2 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 Ag 19 Cu 2 for CO in the eCO 2 RR process is due to the shedding of the -CCAr F ligand from the Ag atom at the very center of the Ag 4 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.