Ligand-Dependent Intracluster Interactions in Electrochemical CO₂ Reduction Using Cu₁₄ Nanoclusters

The electrochemical CO₂ reduction reaction (CO₂RR) has been extensively studied because it can be leveraged to directly convert CO₂ into valuable hydrocarbons. Among the various catalysts, copper nanoclusters (Cu NCs) exhibit high selectivity and efficiency for producing CO₂RR products owing to their unique geometric/electronic structures. However, the influence of protective ligands on the CO₂RR performance of Cu NCs remains unclear. In this study, it is shown that different thiolate ligands, despite having nearly identical geometries, can substantially affect the electrochemical stability of Cu₁₄ NCs in the CO₂RR. Notably, Cu₁₄ NCs protected by 2-phenylethanethiolate exhibit greater stability and achieve a relatively higher selectivity (≈40%) for formic acid production compared with the cyclohexanethiolate-protected counterpart. These insights are crucial for designing Cu NCs that are both stable and highly selective, enhancing their efficacy for electrochemical CO₂ reduction.