Ligand-shell engineering of a Au25 nanocluster boosting CO2 electroreduction to syngas with tunable range proportion

Abstract

Au nanoclusters (NCs) with atomic-level precision represent an ideal model catalyst enabling efficient CO₂-to-chemical conversion, yet the catalytic performance of distinct active sites in Au NCs remains poorly understood. In this work, ligand-shell engineering has been successfully carried out through a “ligand-stripping pyrolysis” strategy to obtain modified Au₂₅ NCs for electrocatalytic CO₂ reduction reaction (eCO₂RR). Significantly, in situ pyrolysis techniques and structural characterization identify that the exposure of S/Au active sites has been precisely controlled during the adjusted thermal decomposition of the Au NCs, which establishs a clear site-product relationship. The CO/H₂ molar ratio can be precisely adjusted across an exceptionally wide range (0.26–25.47) – a span that encompasses key industrially relevant ratios, such as the 1:2 ratio optimal for Fischer-Tropsch synthesis. Molecular dynamics (MD) simulations quantitatively disclose the interaction trend between exposed S/Au sites and CO₂. S sites exhibit a superior CO₂ affinity, with the local CO₂ concentration increasing as S-site density increases, thereby kinetically promoting eCO₂RR. Theoretical calculations also reveal that S sites facilitate the stabilization of *CO₂ and *CO intermediates and promote electron transfer. In contrast, Au sites are energetically more favorable for the hydrogen evolution reaction. This study establishes an ideal platform for investigating structure-performance relationships of atomically precise NCs and provides guidance for designing metal NCs-based catalysts.