Quantitative XPS analysis of bimetallic Cu-Co catalysts

The surfaces of bimetallic Cu-CO/SiO2 catalyst with 1 Cu:2 Co atomic ratio has been studied focusing on the determination of bimetallic phase thicknes s and its distribution using a mathematical formalism from X-ray photoelect ron spectroscopy (XPS) intensities. X-ray diffraction analysis indicated a Cu-Co alloy formation and XPS qualitative analysis showed that Co-0 and Co- 0 species were present on the surface. Atomic ratios of Cu/Si, Co/Si and Co /Cu from XPS and atomic absorption (A.A.) analyses suggested homogeneous pa rticle formation with a slight Cu surface enrichment in the catalyst. A mat hematical model was proposed from relative intensity ratios, which was able to determine the metallic particle thickness and its coverage fraction at the support. Considering that these values were comparable to those for the particle size obtained from transmission electron microscopy (TEM) measure ments, it may be said that the model describes the evaluated system accurat ely.