Tuning Reaction Pathways by Controlling Atomic Assembly on Oxide Clusters.

Precisely controlling the assembly of atomic sites on oxide clusters (< 1 nm) represents an expanded yet challenging strategy for tuning catalytic performance. Here, we construct two well-defined model catalysts, single-atomic Pt on CuOx clusters (Pt1-CuOx/CN) and triple-atomic Pt on CuOx clusters (Pt3-CuOx/CN), and employ methanol oxidation reaction (MOR) as a probe to unravel the role of atomic assembly in governing catalytic mechanisms. Pt1-CuOx/CN enables a CO-free pathway, achieving an ultrahigh formate selectivity of 80%-99% over a wide potential window (0.6-1.0 V vs. RHE). In contrast, Pt3-CuOx/CN follows a hybrid pathway involving both formate and CO routes, delivering significantly higher mass activity than that of Pt1-CuOx/CN and the commercial Pt/C, alongside high resistance to CO poisoning. Isolated Pt sites in Pt1-CuOx/CN impose a prohibitively uphill free-energy change for the key *COH intermediate (2.15 eV), effectively suppressing CO generation. Conversely, triangular Pt sites in Pt3-CuOx/CN form a robust electronic localization center via deep 5d orbital hybridization, facilitating d→π* electron back-donation and stabilizing *COH adsorption in a triple hollow-site configuration, lowering the limiting free-energy requirement for the CO pathway. This work reveals the role of atomic-scale assembly on oxide clusters in dictating catalytic mechanism and performance, opening new avenues for precise design of advanced electrocatalysts.