Temperature-programmed reaction spectroscopy of ceria- and Cu/ceria-supported oxide catalyst

The surface reduction and oxidation of nanocrystalline CeO(2) and CuO/CeO(2) was investigated by temperature-programmed reduction (TPR) and isothermal/temperature-programmed oxidation (TPO) measurements. Samples with Cu concentrations in the range of 5-20% were prepared by homogeneous precipitation and characterized with regard to their composition, structure, and specific surface area. The quantitative analysis of H(2) TPR measurements of the mixed oxides indicated that (i) the majority of the copper component was completely reduced at temperatures below 473 K and (ii) chemisorption of hydrogen occurred at T = 375 K, catalyzed by the copper oxide. The reoxidation of the samples with N(2)O could also be separated into two partial reactions: (i) a reaction of N(2)O with adsorbed hydrogen at room temperature and (ii) the oxidation of the reduced copper component between 343 and 573 K. Annealing of Cu(0.08)Ce(0.92)O(2-x) at temperatures above 1073 K resulted in the precipitation of a copper oxide phase, as was evident from X-ray diffraction (XRD). Changes in the morphology of the copper component, induced by high-temperature annealing, had a significant effect on the N(2)O TPO profile even after annealing at temperatures below 1073 K, where XRD was not sensitive. (C) 2002 Elsevier Science.