ChemInform Abstract: Palladium‐Alumina Catalysts: A Diffuse Reflectance Study.

Abstract

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FTIR Spectroscopy of Adsorbed Probe Molecules for Analyzing the Surface Properties of Supported Pt (Pd) Catalysts

“…The a.b. at 20500 and 39500 cm −1 can be attributed, respectively, to d-d transition and ligand-to-metal charge transfer of Pd 2+ ions in D 4h oxygen environment (Rakai et al, 1992). Evacuation at 300 °C decreases the concentration of Pd 2+ ions in PdO (a decrease in the intensity of a.b.…”

Niobia‐Supported Palladium–Manganese Materials: Synthesis and Structural Investigation

“…After heating in flowing O 2 at 400 °C, this shoulder is shifted to 481 nm (Figure 1c). This can be ascribed to the formation of isolated Pd 2+ ions (or to small palladium–oxygen entities) and not to bulk PdO particles, whose absorption threshold lies in the NIR (bandgap width equal to 0.8 eV) 23. EXAFS experiments were conducted on this sample and on bulk PdO.…”

“…The DRS of the Pd(acac) 2 /Nb 2 O 5 sample after anchoring (Figure 1b) shows a shoulder near 415 nm ascribed to the d–d transition of Pd 2+ and acac ligand charge transfer in Pd(acac) 2 23…”

UV–Vis–NIRandEPRSpectroscopies

“…Several studies have been devoted to Pd-silica [34][35][36][37][38], Pd-alumina [39][40][41], Pd-ceria [42] and Pd-zeolites [43][44][45]. Compared with nickel, palladium has a stronger preference for D 4h symmetry, although lower symmetries cannot be excluded in zeolites [44,45]; d-d transitions, located in the blue and UV ranges, are less distinct from CT.…”

“…However, subsequent studies [64,65] have shown the prominent roles of (i) the distant environment, (ii) the degree of [42] has shown the influence of the nature of the support: whereas CeO 2 -supported Pd 2+ is immediately reduced upon contact with CO, the reduction is very slow and only partial when alumina is the support [39]. For many years, the influence of the local symmetry (generally T d or O h ) has been considered as predominant.…”