Evidence for a carbonate species during CO oxidation on deactivated Rh(111) sup 1

Journal Article · Sun Mar 31 23:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90299-J· OSTI ID:5745000

Peden, C H.F.; Houston, J E ^[1]

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1. Sandia National Laboratories, Albuquerque, NM (USA)

Earlier studies suggested the possibility that the observed changes in reaction kinetics arose from the formation of a surface carbonate species, i.e., Rh-O-(CO{sub 2}), on oxidizing Rh which alters the kinetics and decreases the reaction rate because of the tenacious bonding of this complex. In order to further investigate this suggestion, we have recently performed a high-resolution electron energy loss, HREELS (surface vibrational spectroscopy), study of the intermediate species present on the Rh surface under various reaction conditions in conjunction with temperature-programmed desorption (TPD) measurements. The results provide further evidence that such a carbonate complex is present on the surface after reaction under oxidizing conditions. However, we also observed that under these conditions the surface is hydroxylated, probably arising from the presence of impurity H{sub 2}O or H{sub 2} in the reactor. TPD results confirm the importance of these {minus}OH groups in stabilizing the carbonate complex. For example, CO{sub 2} adsorbed on a 'clean' oxide (prepared by high temperature oxygen exposures in ultrahigh vacuum) was found to desorb at temperatures more than 100{degree}C lower than CO{sub 2} desorption from a hydroxylated Rh-oxide surface. In the latter case, CO{sub 2} desorption likely arises from the reaction-limited decomposition of the carbonate species. In fact, the earlier kinetic studies are most consistent with an overall reaction mechanism for CO oxidation under oxidizing conditions involving the rate-limited decomposition of such a surface-bound carbonate species.

• OSTI ID: 5745000
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 128:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
330702* -- Emission Control-- Carbon Monoxide
54 ENVIRONMENTAL SCIENCES
540120 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AIR POLLUTION CONTROL
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBONATES
CATALYSTS
CATALYTIC CONVERTERS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONTROL
DESORPTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY-LOSS SPECTROSCOPY
EQUIPMENT
HYDROXYL RADICALS
KINETICS
METALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POLLUTION CONTROL
POLLUTION CONTROL EQUIPMENT
RADICALS
REACTION INTERMEDIATES
REACTION KINETICS
RHODIUM
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE CONTROL
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS