Atomically precise alkynyl-protected Ag19Cu2 nanoclusters: Synthesis, structure analysis, and electrocatalytic CO2 reduction application

Abstract

We report the synthesis, structure analysis, and electrocatalytic CO2 reduction application of Ag19Cu2(C≡CArF)12(PPh3)6Cl6 (abbrevaited as Ag19Cu2, C≡CArF: 3, 5-bis(trifluoromethyl)phenylacetylene) nanoclusters. Ag19Cu2 has characteristic absorbance feature, and is a superatomic cluster with 2 free valent electrons. Single-crystal X-ray diffraction (SC-XRD) revealed that, the metal core of Ag19Cu2 is composed of a 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 of current density and FECO 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≡CArF ligand of 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 atomical-level structure-performance relationship in catalytic field.