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Catalysis Letters

, Volume 6, Issue 1, pp 1–12 | Cite as

Thermodynamics of reduction and oxidation reactions on oxidized or reduced Pt supported on γ-Al2O3

  • Xuehao Lin
  • Jack Davis
  • J. J. Fripiat
Article

Abstract

The integral enthalpies of H2 or O2 reactions with oxidized or reduced Pt supported on γ Al2O3 have been measured in a dual calorimeter at 60 ° C. These enthalpies were calculated assuming the formation of Pt x s O and PtsH surface groups and using accepted values of heat of H2 and O2 chemisorption on bare polycrystalline Pt. The calculated and measured reaction enthalpies agree under the following conditions: 1) Pt2O and Pt 2 s O surface stoichiometries are acceptable (1 ⩽ x ⩽ 2) whereas Pt2O2 must be rejected (x = 0.5); 2) the water formed in the reduction or oxidation process must be dissociatively chemisorbed on the γ Al2O3 surface; 3) the spiltover hydrogen is atomic and its enthalpy of combination with surface electron deficient site is about -10 kcal/g atom.

The significance of dispersion measurements is discussed in relation with hydrogen spillover. Neglecting spillover in reduction at 60 ° C leads to unrealistic values of dispersion.

Thermodynamics of Pt oxidation thermodynamics of Pt reduction H spillover H chemisorption 

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Copyright information

© J.C. Baltzer A.G. Scientific Publishing Company 1990

Authors and Affiliations

  • Xuehao Lin
    • 1
  • Jack Davis
    • 1
  • J. J. Fripiat
    • 1
  1. 1.Department of Chemistry and Laboratory for Surface StudiesUniversity of Wisconsin-MilwaukeeMilwaukeeUSA

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