[AuAg₂₆(SR)₁₈S]⁻ Nanocluster: Open Shell Structure and High Faradaic Efficiency in Electrochemical Reduction of CO₂ to CO

For atomically precise metal nanoclusters, distinctive molecular architectures and promising applications are urgently required to be intensively explored. Herein, we have first reported the open shell structure of the [AuAg 26 (S–Adm) 18 S] − nanocluster and its application in the electrochemical reduction of CO 2 . The X-ray crystal structure of the AuAg 26 nanocluster is composed of a AuAg 12 icosahedron kernel and a Ag 14 (SR) 18 S open shell. The shell includes a Ag 6 (SR) 3 S, a Ag 5 (SR) 6, and three Ag(SR) 3 motifs. It is the first time twisty propeller-like Ag 5 (SR) 6 and trefoil-like Ag 6 (SR) 3 S motifs in metal nanoclusters have been observed. Due to the novel open shell configuration of Ag 14 (SR) 18 S, four triangular facets of the kernel are exposed. The AuAg 26 nanocluster shows excellent catalytic activity in the electrochemical reduction of CO 2 to CO. The Faradaic efficiency of CO is up to 98.4% under −0.97 V. The electrochemical in situ infrared study and DFT calculations demonstrate that the open shell structure of the AuAg 26 nanocluster is beneficial to the forming of intermediate COOH* in the electrochemical reduction of CO 2 to CO.