Exafs evidence for direct Rh-Tan+ bonding and coverage of the metal particles in a Rh/Ta2O5 SMSI catalyst

Abstract

. (1989). EXAFS evidence for direct Rh-Tan+ bonding and coverage of the metal particles in a Rh/Ta2O5 SMSI catalyst. Catalysis Letters, 2(4), 211-218. DOI: 10.1007/BF00766209 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. An EXAFS investigation showed that the rhodium particles in a Rh/Ta205 catalyst were fully reduced and in the 'normal' state after reduction in H 2 at 523 K. After reduction at 858 K, in the SMSI state, tantalum ions could be detected in the reduced supporting oxide directly underneath the rhodium metal particles and in tantalum oxide covering the rhodium metal particles. Neither alloy formation, nor the formation of raftlike structures was observed.

Effects of Reduction Temperature and Metal−Support Interactions on the Catalytic Activity of Pt/γ-Al2O3 and Pt/TiO2 for the Oxidation of CO in the Presence and Absence of H2

“…Similar behavior was also observed in Rh/TiO 2 , Rh/Ta 2 O 5 , Ni/Nb 2 O 5 , and Ni/TiO 2 samples. In these cases EXAFS results provide strong evidence for the structural reorganization of the support in the vicinity of the metal particles, enabling a direct bonding between metal atoms and partially reduced cations from the support, as evidenced by the detection of Rh−Ti n + , Rh−Ta n + , Ni−Nb n + , and Ni−Ti n + contributions in the EXAFS spectra. − …”

“…In these cases EXAFS results provide strong evidence for the structural reorganization of the support in the vicinity of the metal particles, enabling a direct bonding between metal atoms and partially reduced cations from the support, as evidenced by the detection of Rh-Ti n+ , Rh-Ta n+ , Ni-Nb n+ , and Ni-Ti n+ contributions in the EXAFS spectra. [36][37][38] CO Adsorption on Pt. Additional information regarding the state of Pt in Pt/TiO 2 and Pt/γ-Al 2 O 3 can be obtained from the FTIR spectra recorded during the adsorption and desorption of CO as a probe molecule.…”