4f-Electron localization in Ce-embedded Co₆Te₈ clusters for enhanced CO₂ reduction catalysis

Density functional theory (DFT) calculations were employed to investigate the CO₂ reduction reaction (CO₂RR) on a series of metal-embedded Co₆Te₈(PH₃)₅ chalcogenide clusters, incorporating transition metals and f-block elements including Ti (3d), Zr (4d), Hf (5d), Ce (4f/5d), and Th (5f/6d). Structural modifications introduced by metal embedding were found to effectively tune the electronic structure, thereby altering the reactivity of the host cluster. Subsequently the interplay between f and d orbitals was systematically analyzed to reveal its role in modulating catalytic activity. Among all candidates, Ce@Co₆Te₈(PH₃)₅ exhibits the lowest endothermic energy along the CO₂RR pathway, suggesting its superior catalytic performance. This behavior arises from the unique participation of Ce 4f states, which enhance both π* antibonding population and Pauli repulsion at the Co-CO interface. These two effects jointly weaken the net interaction, making CO desorption most favorable on Ce@cage and thereby accelerating the catalytic cycle. Additionally, 4f electron localization narrows the HOMO-LUMO energy gap, further increasing the electronic reactivity of the cluster. These findings highlight 4f electron localization as a key descriptor for designing high-performance molecular catalysts based on chalcogenide clusters.