Probing active sites on Pd/Pt alloy nanoparticles by CO adsorption

We studied the adsorption of CO on PdPt nanoparticles with different metal ratio using theoretical calculations (DFT) and experimental investigations. A model catalyst was employed, where platinum (Pt) and palladium (Pd) were co-deposited via physical vapor deposition on the surface of α-Al2O3(0001). CO was used as a probe molecule for the particles’ surface composition. Polarized infrared reflection absorption spectroscopy (FT-IRRAS) enabled the observation of CO adsorption on top and side facets. The role of the Pd/Pt alloy ratio on the adsorption was investigated by comparing the FT-IRRAS data for different alloy arrangements and pure Pd and Pt nanoparticles. The dependence of the IR bands on the local atomic pattern was investigated via DFT calculations, revealing that both bulk alloy composition, as well as nearby atoms, influence the wavenumber of the bands.