High resolution EELS measurements of CO adsorption on Pt/Al2O3 model catalysts via impact scattering

The use of high resolution electron energy loss spectroscopy (EELS) to study adsorption on model supported metal catalysts is investigated, using CO adsorption on Pt/Al2O3 as a simple test case. The model catalysts are formed by evaporating Pt onto an oxidized, polycrystalline, aluminum foil. Transmission electron microscope pictures show that the model catalyst consists of metal particles of average diameter 1.1–1.3 nm covering 18%–25% of the surface area of the support. EELS spectra recorded for specular and off-specular electron scattering reveal that the strong loss peaks due to vibrations of the smooth substrate occur via inelastic dipole scattering, but that the loss peaks due to CO adsorbed on the rough particles occur via the inelastic impact scattering mechanism. This has important implications for the use of EELS to study model supported metal catalysts.