Theoretical predictions of platinum-rhodium bimetallic catalysts
After a general introduction to supported bimetallic catalysts and automobile catalytic converters (supports, base metal promoters, noble metals, deterioration of 3-way catalysts, current/future technology), a paper is presented for surface segregation in bimetallic catalysts: The catalytic properties are influenced by the structure of the cluster surface. Two methods are described to treat this problem, from the demanding corrected effective medium (CEM) theory (a non-self-consistent density functional based method) and the simple method of surface modified pair potentials. Predictions are compared with experiment for the heat of formation in Rh[sub x]Pt[sub 1[minus]x] alloys and for surface segregation in Rh[sub 0.9]Pt[sub 0.1](111). Results on shape, site composition, surface micromixing are shown for 201 atom clusters (dispersion of 0.6) and Rh[sub x]Pt[sub 1[minus]x](111). The CEM calculated cohesive energy of Rh is slightly smaller than for Pt, but the surface energy of Rh is larger: the driving force for surface segregation is the relative surface energies, not the relative cohesive energies. One can predict surface energy differences by accounting for the variation of the bond energy with coordination. Recommendations for the development of improved automobile exhaust catalysts are given. The Monte Carlo bimetallic simulation program is described.
- Research Organization:
- Ames Lab., IA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6727273
- Report Number(s):
- IS-T-1635; ON: DE93007540
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hydrogen adsorption behavior and strong metal-support interaction (SMSI) on Rh-Pt bimetallic catalysts
Platinum-rhodium synergism in three-way automotive catalysts
Related Subjects
330700* -- Advanced Propulsion Systems-- Emission Control
36 MATERIALS SCIENCE
360104 -- Metals & Alloys-- Physical Properties
54 ENVIRONMENTAL SCIENCES
540120 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
ALLOYS
CATALYSTS
CATALYTIC CONVERTERS
CATALYTIC EFFECTS
DISPERSIONS
ENERGY
ENTHALPY
EQUIPMENT
FORMATION HEAT
FREE ENERGY
MATERIALS
PHYSICAL PROPERTIES
PLATINUM ALLOYS
PLATINUM METAL ALLOYS
POLLUTION CONTROL EQUIPMENT
REACTION HEAT
RHODIUM ALLOYS
SEGREGATION
SOLID CLUSTERS
SURFACE ENERGY
SURFACE PROPERTIES
SURFACES
THERMODYNAMIC PROPERTIES