Influence of hydrogen chemisorption on the surface composition of Pt-Rh/Al{sub 2}O{sub 3} catalysts

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1996.0285· OSTI ID:494279

Savargaonkar, N; King, T S ^[1]; Pruski, M ^[2]

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1. Iowa State Univ., Ames, IA (United States)
2. Ames Lab., IA (United States); and others

The surface compositions of a series of platinum-rhodium bimetallic catalysts supported on {gamma}-alumina were determined in the presence of chemisorbed hydrogen by {sup 1}H NMR spectroscopy. The surface compositions of hydrogen-covered Pt-Rh bimetallic catalysts were found to be slightly enriched in Rh, significantly different from the surface compositions of adsorbate-free Pt-Rh surfaces, which are enriched in Pt. Further, based on selective excitation NMR experiments it was found that bimetallic particles of fairly uniform compositions were formed. Atomistic simulations of hydrogen-covered Pt-Rh bimetallic catalysts were done using a method that involved coordination-dependent bond energies. The simulations indicated that the heat of adsorption of hydrogen on rhodium is about 13 kJ/mol higher than that on platinum. Finally, a general, qualitative method for predicting the influence of adsorbates on the surface segregation behavior of bimetallic systems is described on the basis of knowledge of the surface energies at various sites and the heats of adsorption. 35 refs., 6 figs., 3 tabs.

• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 494279
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 162; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ABSORPTION HEAT
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHEMISORPTION
HETEROGENEOUS CATALYSIS
HYDROGEN
MATHEMATICAL MODELS
NUCLEAR MAGNETIC RESONANCE
PLATINUM
RHODIUM
SORPTIVE PROPERTIES
STRUCTURAL CHEMICAL ANALYSIS