Microstructures of Pt-Ce and Rh-Ce particles on alumina and silica

Journal Article · Sun Nov 01 04:00:00 EST 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90023-B· OSTI ID:5601832

Schwartz, J M; Schmidt, L D ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

The effects of adding Ce to 20-200 [angstrom] diameter particles of Pt and Rh on planar Al[sub 2]O[sub 3] and SiO[sub 2] substrates are examined using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron energy-loss spectroscopy (EELS), following treatments in H[sub 2] and O[sub 2] atmospheres. Samples were transferred repeatedly between furnace and TEM so that the time evolution of the microstructure of individual particles could be followed. TEM shows that upon heating Pt alone on Al[sub 2]O[sub 3] or SiO[sub 2] in H[sub 2], Pt forms cubic particles, while when Pt and Ce are codeposited, the Pt particles are about the same size but no longer have square outlines. XPS shows that the Pt peak shifted to Pt[sup +2] when heated in O[sub 2] on both Al[sub 2]O[sub 3] and SIO[sub 2] when Ce was present and returned to Pt[sup 0] after heating in H[sub 2]. The Pt particles tend to shrink or disappear after heating in O[sub 2] at 650[degrees]C, and this is much faster without Ce, showing that Ce retards the volatilization of Pt oxides. When Rh-Ce on Al[sub 2]O[sub 3] of SiO[sub 2] is heated in H[sub 2], Rh forms particles of no preferred shape. After heating in O[sub 2] to 600[degrees]C, Rh oxidizes to Rh[sub 2]O[sub 3] and remains particulate on Al[sub 2]O[sub 3], but spreads to a film on SiO[sub 2] in the presence of Ce. Upon reduction, Rh[sub 2]O[sub 3] reduces to metallic Rh and forms particles of approximately the same size as the original particles on Al[sub 2]O[sub 3] and larger than the original size on SiO[sub 2]. Ce[sub 2]Si[sub 2]O[sub 7] has been characterized on SiO[sub 2] adjacent to Rh particles after reduction of an oxidized sample, but CeAlO[sub 3] has not been observed on Al[sub 2]O[sub 3]. 32 refs., 6 figs.

• OSTI ID: 5601832
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 138:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
330700 -- Advanced Propulsion Systems-- Emission Control
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALLOYS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYST SUPPORTS
CERIUM ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ENERGY-LOSS SPECTROSCOPY
MICROSCOPY
MICROSTRUCTURE
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARTICLES
PHOTOELECTRON SPECTROSCOPY
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
RARE EARTH ALLOYS
REDUCTION
RHODIUM ALLOYS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SPECTROSCOPY
TRANSMISSION ELECTRON MICROSCOPY