title: Growth and decomposition of aligned and ordered PdO nanoparticles.
abstract: The formation, thermal decomposition, and reduction of small PdO particles were studied by high-resolution transmission electron microscopy and selected area electron diffraction. Well-defined Pd particles (mean size of 5-7 nm) were grown epitaxially on NaCl (001) surfaces and subsequently covered by a layer of amorphous SiO2 (25 nm), prepared by reactive deposition of SiO in 10(-2) Pa O2. The resulting films were exposed to molecular O2 in the temperature range of 373-673 K, and the growth of PdO was studied. The formation of a PdO phase starts at 623 K and is almost completed at 673 K. The high-resolution experiments suggest a topotactic growth of PdO crystallites on top of the original Pd particles. Subsequent reaction of the PdO in 10 mbar CO for 15 min and thermal decomposition in 1 bar He for 1 h were also investigated in the temperature range from 373 to 573 K. Reductive treatments in CO up to 493 K do not cause a significant change in the PdO structure. The reduction of PdO starts at 503 K and is completed at 523 K. In contrast, PdO decomposes in 1 bar He at around 573 K. The mechanism of PdO growth and decay is discussed and compared to results of previous studies on other metals, e.g., on rhodium.
authors.affiliation: Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria. simon.penner@uibk.ac.at
authors.forename: Simon
authors.initials: S
authors.lastname: Penner
authors.forename: Di
authors.initials: D
authors.lastname: Wang
authors.forename: Bernd
authors.initials: B
authors.lastname: Jenewein
authors.forename: Harald
authors.initials: H
authors.lastname: Gabasch
authors.forename: Bernhard
authors.initials: B
authors.lastname: Klötzer
authors.forename: Axel
authors.initials: A
authors.lastname: Knop-Gericke
authors.forename: Robert
authors.initials: R
authors.lastname: Schlögl
authors.forename: Konrad
authors.initials: K
authors.lastname: Hayek