Impact of Heterocore Atoms on CO₂ Electroreduction in Atomically Precise Silver Nanoclusters

Understanding the effect of internal atoms in metal nanoparticles on heterogeneous catalytic processes is crucial for achieving high activity and selectivity. This requires meticulous synthetic control over the size, composition, and atomic arrangement of nanoparticles. Here, we report the design of ligand-exchange-induced structure transformation and nanomolecule-templated atomic-level galvanic exchange strategies to synthesize PtAg₂₄(IPBT)₁₈ (denoted as PtAg₂₄) and AuAg₂₄(IPBT)₁₈ (denoted as AuAg₂₄) nanoclusters (NCs). Both NCs exhibit identical total metal atom and ligand (IPBT: 2-isopropylbenzenethiolate) counts, as well as atomic-level structure, except for the difference in the core atom (Pt and Au). Using these model NCs, we uncover the impact of heterocore atoms on the electrochemical CO₂ reduction reaction (eCO₂RR) activity and selectivity. The central Pt atom in PtAg₂₄ is less favorable for eCO₂RR activity, with an activity approximately 4 times smaller than that of Au in AuAg₂₄. The eCO₂RR product CO selectivity is <30% for PtAg₂₄, while it exceeds 70% for AuAg₂₄, revealing the critical role of the central atom in surface catalytic pathways. Furthermore, AuAg₂₄ exhibits high activity, with a CO partial current density of -202.2 mA cm^-2, and stability over 24 h, retaining 90% CO selectivity in a membrane electrode assembly configuration. <i>Operando</i> spectroscopy and density functional theory calculations suggest the weaker adsorption of *CO intermediates and smaller energy barrier facilitate CO production on AuAg₂₄ compared to PtAg₂₄, providing valuable atomistic insights into the reaction intermediates and mechanism. The findings in this work will inspire the design of more atomically precise model nanocatalysts to explore the role of their remarkable features in the catalytic activity and selectivity for renewable energy conversion and storage.