The interaction of Rh with intrinsic defects of reduced Rh/CeO{sub 2} catalysts: A comparative XPS/UPS and {sup 1}H-NMR study
- Universitaet Tuebingen (Germany); and others
X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) as well as {sup 1}H nuclear magnetic resonance ({sup 1}H-NMR) experiments are reported on Rh surface-doped CeO{sub 2} (111)-oriented thin films and powder samples that are reduced with H{sub 2} at temperatures between 293 and 873 K. Two reduction processes at T {le} 573 K and T > 573 K are found which lead to two distinguishable states of the surface. These temperature regimes are denoted here as low temperature reduction (ltr) and high temperature reduction (Itr). In the ltr-regime the surfaces become hydroxylated and Ce{sup 3+} ions are formed as concluded from XPS. Correspondingly two{sup 1}H-NMR signals of hydrogen that is chemisorbed on Rh and on CeO{sub 2} are detected. In the htr-regime, CeO{sub 2-x} surfaces are by far less hydroxylated, which results from the desorption of H{sub 2}O and the formation oxygen vacancies. Simultaneously, Rh loses its hydrogen adsorption capability, whereas this property is practically constant in the ltr-regime. These findings are correlated to UPS measurements that give evidence for an electronic charge transfer from the CeO{sub 2-x} surface to Rh atoms. Finally this effect is interpreted in terms of the interaction between Rh atoms and oxygen vacancies at the CeO{sub 2-x} surface.
- OSTI ID:
- 468024
- Report Number(s):
- CONF-960652-; TRN: 96:004817-0061
- Resource Relation:
- Conference: 11. international congress on catalysis (ICC-11), Baltimore, MD (United States), 30 Jun - 5 Jul 1996; Other Information: PBD: 1996; Related Information: Is Part Of 11th International congress on catalysis - 40th anniversary. Part A and B; Hightower, J.W.; Delgass, W.N.; Iglesia, E.; Bell, A.T. [eds.]; PB: 1482 p.
- Country of Publication:
- United States
- Language:
- English
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