Changes in the electronic structure of platinum−3d transition single-crystal alloys (Pt1 - x M x with M = Fe, Co, and Ni) are studied as a function of composition, order and nature of the 3d metal. These changes are detected by using synchrotron radiation to analyze the absorption edges. Both the Pt LII and LIII edges and the 3d metal K edge exhibit correlated changes, which are most sensitive to the minority element in the alloy. The modifications on the Pt LII and LIII edges are interpreted as resulting from a variation of the number of holes in the 5d band, corresponding to an electron transfer to platinum from the 3d metal. The corresponding changes observed on the 3d metal K edge point to a population rearrangement between the probed levels originating from the atomic 3d, 4s, and 4p levels. An effect of ordering has also been observed in the Pt−Co alloys the magnitude of which is greater at the Co K-edge for the lowest concentration of this element. Finally, we compare our results to available calculations and experimental results obtained by other techniques.

The Al2O3-TiO2 (1:1.3 mole ratio) was obtained from dilute mixture solutions of sodium aluminate and titanium tetrachloride by hydrolysis with in situ generated ammonium hydroxide. The calcined (773 K) mixed oxide powder was constituted from nanosized anatase crystallites and amorphous alumina. A nominal 16 wt % V2O5 was impregnated on the calcined Al2O3-TiO2 support by using an oxalic acid solution of NH4VO3. To investigate thermal stability of Al2O3-TiO2 and the dispersion of vanadia on its surface these samples were subjected to thermal treatments from 773 to 1073 K and were examined by X-ray photoelectron spectroscopy, X-ray diffraction, FT-infrared, and O2 chemisorption techniques. The physicochemical characterization results revealed that the Al2O3-TiO2 mixed oxide is homogeneous and accommodates a monolayer equipment of V2O5 in a highly dispersed state when calcined at 773 K. The Ti/Al atomic ratio as determined by XPS suggests a coverage of Al2O3 by TiO2. However, at higher calcination temperatures surface enrichment of alumina occurs due to a concentration gradient. In the case of the V2O5/Al2O3-TiO2 sample, an increase of calcination temperature also resulted in the decrease of specific surface area and the dispersion of vanadium oxide. The impregnated vanadium oxide also exhibited a noticeable influence on the phase transformation of titania anatase. The V/Ti and V/Al atomic ratios revealed that vanadium oxide is distributed equally on both tiania and alumina surfaces when calcined at 773 K; however, surface segregation of vanadium oxide occurred on the titania surface at higher calcination temperatures.