Metallic states of Pt/CeO ₂ catalysts dictate the activity for CO oxidation

Pt/CeO2 is a typical catalyst for CO oxidation, whose understanding of the structure-performance relationship and the factors dictating the activity remains to be fully elucidated. In this work, three Pt/CeO2 catalysts with distinct Pt architectures, namely single atoms (denoted as Pt1), nanoclusters (~1.0 nm, denoted as PtCL), and nanoparticles (~3.5 nm, denoted as PtNP), were investigated using aberration-corrected scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), CO pulse chemisorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ-DRIFTS). The results show that Pt nanoparticles exhibit the lowest oxidation state, strongest CO adsorption, and highest turnover frequency (TOF), substantially outperforming Pt clusters and single atoms. According to kinetic analysis, metallic Pt favors a Mars-van Krevelen pathway featuring efficient CO activation and carbonate-mediated turnover. In contrast, isolated Pt2+ atoms show weak CO binding and a distinct but less active regime. It is revealed that the metallic state of Pt, rather than dispersion alone, dictates the catalytic activity for CO oxidation on Pt/CeO2, which offers guidance for designing the next generation of high-performance Pt/CeO2 catalysts.