Influence of the hydrogen uptake by the support on metal-support interactions in catalysts. Comparison of the Rh/TiO/sub 2/ and Rh/SrTiO/sub 3/ systems
Samples of Rh/TiO/sub 2/ and Rh/SrTiO/sub 3/ catalysts subjected to thermal treatments under H/sub 2/ and in vacuo have been examined by NMR, EPR, and quantitative adsorption techniques in order to ascertain the dependence of SMSI effects on hydrogen strongly adsorbed at high temperatures. Loss of H/sub 2/ chemisorption capacity upon high-temperature reduction (monitored directly by NMR of metal-adsorbed hydrogen) occurs only in Rh/TiO/sub 2/, and is accompanied by extensive incorporation of hydrogen in the support in form of hydride-type species. Both effects are reversed by high-temperature outgassing, while the amount of EPR-detected Ti/sup 3 +/ increases. It is concluded that support-held hydrogen produces SMSI-type effects in Rh/TiO/sub 2/ that cannot be explained by a conventional support reduction mechanism (generation of Ti/sup 3 +/ and anion vacancies) or by coverage of the metal with TiO/sub x/ species migrating from the support. Electronic changes (rehybridization) induced in the small metal particles by interaction with highly reduced species generated at the support are proposed as a possible source of SMSI behavior that can be reversed by outgassing or oxidation more easily than coverage by TiO/sub x/ entities. 40 references, 8 figures.
- Research Organization:
- Instituto de Fisico-Quimica Mineral, Madrid, Spain
- OSTI ID:
- 6038054
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 89:25
- Country of Publication:
- United States
- Language:
- English
Similar Records
EPR characterization of Ti sup 3+ ions at the metal-support interface in Pt/TiO sub 2 catalysts
Structure of a Rh/TiO/sub 2/ catalyst in the strong metal-support interaction state as determined by EXAFS
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
HYDROGEN
ADSORPTION
RHODIUM
PERFORMANCE
STRONTIUM TITANATES
SORPTIVE PROPERTIES
TITANIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
ELECTRON SPIN RESONANCE
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
HIGH TEMPERATURE
NUCLEAR MAGNETIC RESONANCE
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
DATA
ELEMENTS
INFORMATION
MAGNETIC RESONANCE
METALS
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
RESONANCE
SORPTION
STRONTIUM COMPOUNDS
SURFACE PROPERTIES
TITANATES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties