(376bo) Stability of Ligand Protected Au Nanoclusters Under Electrochemical Reduction of CO2

Authors: 
Nagarajan, A. V., University of Pittsburgh
Juarez-Mosqueda, R., University of Pittsburgh
Cowan, M., University of Pittsburgh
Mpourmpakis, G., University of Pittsburgh
Ligand-protected gold nanoclusters (NCs) are a novel class of particles that have attracted great interest in the field of catalysis due to their atomically precise structure, high surface area-to-volume ratio, and unique electronic structure. In particular, the anionic thiolate-protected Au25 NC, [Au25(SR)18]1-, with partially lost ligands, has been demonstrated to act as an active catalyst for the electrochemical reduction of CO21, 2. However, the stability of this and other thiolate-protected NCs after partial ligand removal remains elusive. Using density functional theory (DFT) calculations and the recently developed thermodynamic stability model (TSM)3, we investigate the stability of [Au25(SR)18]1-, [Au18SR14]0, [Au23(SR)16]1-, and [Au28(SR)20]0 NCs when a single ligand (–R or –SR) is removed from the surface. Additionally, we examine the stability of the partially protected NCs upon the adsorption of CO2 reduction reaction intermediates (H, CO, and COOH) on the S or Au active site generated after single –R or –SR ligand removal respectively. Our results reveal that the partially protected Au25 NC shows the highest stability compared to the other partially protected NCs. Additionally, we find that the presence of the COOH intermediate on the Au or S active sites stabilizes the Au25 NC as the removed ligand, which agrees with experimental observations on the stability of these NCs under electrochemical conditions. This study offers molecular level insights into the stability of ligand-protected gold NCs during the electrochemical reduction of CO2 to CO.

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