[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 [AuAg26(S–Adm)18S]− nanocluster and its application in the electrochemical reduction of CO2. The X-ray crystal structure of the AuAg26 nanocluster is composed of a AuAg12 icosahedron kernel and a Ag14(SR)18S open shell. The shell includes a Ag6(SR)3S, a Ag5(SR)6, and three Ag­(SR)3 motifs. It is the first time twisty propeller-like Ag5(SR)6 and trefoil-like Ag6(SR)3S motifs in metal nanoclusters have been observed. Due to the novel open shell configuration of Ag14(SR)18S, four triangular facets of the kernel are exposed. The AuAg26 nanocluster shows excellent catalytic activity in the electrochemical reduction of CO2 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 AuAg26 nanocluster is beneficial to the forming of intermediate COOH* in the electrochemical reduction of CO2 to CO.针对原子级精确金属纳米团簇，亟需深入探索其独特的分子架构与极具潜力的应用场景。本文首次报道了[AuAg26(S-Adm)18S]⁻纳米团簇的开壳层结构及其在CO₂电化学还原中的应用。AuAg26纳米团簇的X射线晶体结构由AuAg12二十面体核与Ag14(SR)18S开壳层构成，该开壳层包含Ag6(SR)3S、Ag5(SR)6以及三个Ag(SR)3基元。本研究首次在金属纳米团簇中观测到螺旋桨状的Ag5(SR)6与三叶状的Ag6(SR)3S基元。得益于Ag14(SR)18S独特的开壳层构型，该团簇核的四个三角晶面得以暴露。AuAg26纳米团簇在CO₂电化学还原为CO的反应中展现出优异的催化性能：在-0.97 V电位下，CO的法拉第效率最高可达98.4%。电化学原位红外光谱研究与密度泛函理论（DFT）计算结果表明，AuAg26纳米团簇的开壳层结构有助于CO₂电化学还原为CO过程中COOH*中间体的生成。