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Nature of the two-step temperature-programmed decomposition of PdO supported on alumina

Paper ID Volume ID Publish Year Pages File Format Full-Text
39859 45837 2014 7 PDF Available
Title
Nature of the two-step temperature-programmed decomposition of PdO supported on alumina
Abstract

•PdO on alumina decomposes in a two-step process during thermal ramping.•Decomposition initiates at the PdO surface near the bulk PdO decomposition temperature forming a Pd shell.•The remaining PdO core decomposes at temperatures above the bulk PdO decomposition temperature.

Temperature-programmed decomposition of PdO supported on high-surface-area alumina occurs in a two-step process starting near the temperature of bulk PdO decomposition, but slowing to near-zero rates as the bulk oxide decomposition temperature is traversed. Most of the oxide decomposes in a second step 40–60 °C above the bulk PdO decomposition temperature. We present evidence suggesting that a thin Pd shell forms initially on the surface of PdO particles and propose that the resulting core–shell structure is connected with the observed meta-stability. Both the experimental results and order-of-magnitude estimates indicate that neither small particle effects (metal-support interaction or surface energy) nor low oxygen permeability through the Pd shell explain the two-step process. We tentatively ascribe the higher-temperature PdO decomposition step to the contribution of strain energy to the Pd shell imparted by epitaxy with the underlying PdO lattice.

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Keywords
Palladium oxide (PdO); Decomposition; Thermogravimetric analysis (TGA); X-ray diffraction (XRD); Scanning transmission electron microscopy (STEM)
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Nature of the two-step temperature-programmed decomposition of PdO supported on alumina
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 475, 5 April 2014, Pages 420–426
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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