Atomically Precise Cu(I) Clusters Facilitated by CeO-Derived Reverse Hydrogen Spillover for Selective Electrochemical CO Methanation.

Atomically precise Cu clusters with stabilized low-coordinated Cu species demonstrate promising deep CO reduction capability, although product selectivity requires enhancement. To address this, two Cu clusters, Cu(PPh)(PET) and [CuS(PPh)(PET)] (denoted as Cu and Cu, respectively) were constructed via ligand-mediated assembly of Cu triangular units. Both clusters effectively catalyze deep CO reduction, with CH as the dominant product (FE = 60.8 ± 1.6% at -1.4 V for Cu and 50.5 ± 4.3% at -1.5 V for Cu). Notably, CeO incorporation dramatically enhances CH selectivity, elevating FE to 78.5 ± 0.4% at -1.3 V for Cu/CeO and 64.3 ± 1.9% at -1.4 V for Cu/CeO. XAS and XPS analysis validate stabilized Cu species within Cu clusters under CORR, favoring *CO intermediate stabilization. Kinetic analysis identifies isolated Cu sites within Cu clusters as the active center for both CH and CH formation, mediating the hydrogenation reaction via the Langmuir-Hinshelwood mechanism while suppressing C-C coupling. Theoretical calculations elucidate that CeO facilitates water activation to generate abundant *H species, which subsequently migrate to sulfur sites in Cu clusters through a reverse hydrogen spillover mechanism. This synergistic process significantly accelerates *CO hydrogenation kinetics, thereby enhancing the CH selectivity.