Characterization of niobia-supported palladium-cobalt catalysts

Niobium oxide supported Pd-Co catalysts were characterized through XPS (X-r ay photoelectron spectroscopy), (XPS), temperature-programmed reduction (TP R), magnetic measurements, X-ray diffraction, and extended X-ray absorption fine structure (EXAFS). XPS analyses suggested the presence of Co3O4 parti cles and Co2+ surface phase. TPR and magnetic measurements showed that the palladium addition promoted not only the reduction of Co3O4 particles but a lso the cobalt surface phase. Magnetic measurements and EXAFS analyses reve aled the Pd-Co alloy formation during reduction. A model represented by bim etallic particles enriched with palladium and particles containing only cob alt was proposed.