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

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.