Dynamics of CeO2-Supported Pt Nanoparticles in CO Oxidation Reaction Revealed by Millisecond Time-Resolved HERFD-XANES Spectroscopy

Abstract

The dynamics of CeO₂-supported 1.5-nm Pt nanoparticles (Pt/CeO₂) during catalysis for CO oxidation at 50 °C were observed. High-energy resolution fluorescence-detected (HERFD) Pt L₃-edge X-ray absorption near-edge structure (XANES) spectroscopy with millisecond time resolution was used for this observation. A series of time-resolved spectra of Pt/CeO₂ during CO oxidation were fitted by linear combinations of spectra corresponding to bare Pt, CO-adsorbed Pt, and oxidised Pt nanoparticles. The analysis revealed that after O₂ pulse injection into CO-adsorbed Pt nanoparticles, all adsorbed CO was oxidised within 0.5 s, forming a bare Pt surface. Subsequently, the bare Pt surface was oxidised at a much slower rate, approximately 10 s, compared with the oxidation of adsorbed CO. These findings demonstrate the utility of time-resolved HERFD-XANES spectroscopy in studying catalytic processes. This reveals variations in the Pt surface state and the kinetics of CO and Pt oxidation on Pt/CeO₂ during the CO oxidation reaction.