In situ study of oxidation states and structure of 4Â nm CoPt bimetallic nanoparticles during CO oxidation using X-ray spectroscopies in comparison with reaction turnover frequency

► In situ NEXAFS characterization of 4 nm CoPt nanoparticles under the cycling total pressure (up to 60 Torr) and reaction temperature of the reactant gases. ► Ambient pressure XPS shows evidence of surface segregation of Co in the CO oxidation condition. ► Turnover frequency is correlated to the AP-XPS and in situ NEXAFS results.