Dual-Ligand Engineering Induces Partial Cu(0) Character in a 2-Electron [Cu ₈ H ₄ (PPh ₂ Py) ₂ (PPh ₂ Py-CH ₃ ) ₄ ] ²⁺ Cluster for Enhanced CO ₂ Electroreduction

Copper-based nanoclusters are promising electrocatalysts for CO₂ reduction (eCO₂RR), where the surface structure and electronic properties critically determine performance. The introduction of the PPh₂Py-CH₃ ligand effectively tailors the Cu₈ surface, modulating its electronic configuration and optimizing the eCO₂RR activity. Coprotection with PPh₂Py and PPh₂Py-CH₃ enables the synthesis of the two-electron cluster [Cu₈H₄(PPh₂Py)₂(PPh₂Py-CH₃)₄]²⁺. Compared with the isostructural zero-electron [Cu₈H₆(PPh₂Py)₆]²⁺ and [Cu₈H₆(PPh₃)₂(PPh₂Py-CH₃)₄]²⁺ analogues, the two-electron form exhibits concurrent geometric and electronic modulation, along with fewer hydrides. Electrochemical measurements reveal that [Cu₈H₄(PPh₂Py)₂(PPh₂Py-CH₃)₄]²⁺ achieves the highest CO Faradaic efficiency (80.0% at -1.0 V vs RHE), outperforming the other clusters. Density functional theory calculations attribute this enhancement to the low atomic dipole-corrected Hirshfeld atomic charge (ADCH) and partial Cu(0) character of the active site, which facilitates CO₂ adsorption and lowers the *COOH formation barrier. This work demonstrates that ligand-induced surface reconstruction is an effective approach to tune Cu cluster catalysts for the high-performance eCO₂RR.