Curvature-induced reaction pathway switching of CO oxidation on Pt1/Pt2 anchored CeO2 nanotubes: a first-principles study.

In this study, we systematically investigated the structure-activity relationship of Pt single-atom (Pt@NT) and diatomic (Pt2@NT) catalysts supported on cerium dioxide nanotubes (CeO2 NTs) with different curvatures for CO oxidation reactions via density functional theory (DFT) calculations, focusing on curvature regulation of surface catalytic reactivity. We constructed CeO2 NT models with inner diameters of (6, 6), (7, 7) and (8, 8), and found that CO oxidation occurs on the internal walls of these NTs and proceeds via the Mars-van Krevelen (MvK) mechanism. The crucial reaction intermediate OCOO presents two configurations, namely armchair OCOO-A and zigzag OCOO-Z. OCOO-Z can be directly generated on Pt@(6, 6) NT, Pt@(8, 8) NT and Pt2@(6, 6) NT, while the formation of OCOO-Z on Pt@(7, 7) NT, Pt2@(7, 7) NT and Pt2@(8, 8) NT requires an isomerization process from OCOO-A to OCOO-Z. Pt@(6, 6) NT delivers the optimal catalytic performance. The energy barrier of its rate-determining step, which corresponds to CO2 production from OCOO-Z, is as low as 0.43 eV, with a corresponding reaction rate constant of 3.35 × 105 s-1. This outstanding performance is attributed to the synergistic effect between the strong confinement induced by high nanotube curvature and the low-coordination Pt active sites. While diatomic Pt2 sites optimize the electronic structure of the catalysts through charge recombination, the small-diameter single-atom system exhibits prominent advantages owing to its unique coordination environment. This work establishes a new mechanism of curvature-induced reaction path switching, and provides solid theoretical guidance for the rational design of high-efficiency CO oxidation catalysts.