Elucidating the stability of ligand‑protected Au nanoclusters under electrochemical reduction of CO_2

摘要

Ligand-protected gold nanoclusters are a novel class of particles that have attracted great interest in the field of catalysisdue to their atomically-precise structure, high surface-to-volume ratio, and unique electronic properties. In particular, theanionic thiolate-protected Au_(25)nanocluster (NC), [Au_(25)(SR)_(18)]~(1−), with partially lost ligands, has been demonstrated to actas an active catalyst for the electrochemical reduction of CO_2.However, the stability of this and other thiolate-protectedNCs after partial ligand removal remains elusive. Using density functional theory (DFT) calculations and the recentlydeveloped thermodynamic stability model, we investigate the stability of [Au_(25)(SR)18]~(1−), [Au_(18)(SR)~(14)]~0, [Au_(23)(SR)_(16)]~(1−), and[Au_(28)(SR)_(20)]~0 with ligand loss. Additionally, we examine the stability of the partially protected NCs upon adsorption of CO_2reduction reaction intermediates (i.e. H, CO, and COOH) on the different active sites generated after ligand removal. Ourresults reveal that the partially protected Au_(25)NC shows the highest stability compared to the other partially protectedNCs in the presence of electrochemical reduction intermediates. We find that the presence of the COOH intermediateon the generated active sites stabilizes the Au_(25)NC almost as well as the removed ligands. Moreover, time-dependentDFT calculations and UV–Vis/Raman experiments suggest that the most probable ligand removal mode under electrochemicalconditions is the one that generates S active sites, in agreement with the DFT ligand removal thermodynamicanalysis. Importantly, this study demonstrates the robustness of the Au_(25)NC and offers a novel way to address stabilityof ligand protected NCs during electrocatalytic reaction conditions.