Performance of Ceria Supported Monometallic and Bimetallic Single-atom Catalysts in Carbon Monoxide Oxidation
Open Access
- Author:
- Pantelis II, Nicholas
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Robert Rioux, Thesis Supervisor
Scott Thomas Milner, Thesis Honors Advisor - Keywords:
- Heterogeneous catalysis
catalysis
single atoms
ceria
palladium
platinum
nickel
adatoms
oxidation
kinetics
bimetallic
monometallic
catalyst
DRIFTS
Arrhenius
Mars van Krevelen
reaction order
ICP
nanoparticles
activity
specific activity - Abstract:
- Research into atomically-dispersed metal catalysts on metal-oxide supports like ceria and alumina has grown significantly due to these catalysts’ increased performance relative to bulk, nanoparticle, and sub-nanometer metal catalysts. Atomically dispersed, single atom catalysts have been shown to increase the specific activity of metal catalysts on metal-oxide supports. This study mainly focuses on difference in kinetic behavior of single-atom palladium, platinum, and nickel adatoms supported on ceria support during the oxidation of carbon monoxide. The relationship between metal weight-loading on a ceria support, reactor temperature, and reaction order was described. Bimetallic single atom catalysts of palladium and platinum on ceria were studied to compare to monometallic systems in terms of activity. Catalysts were characterized using ICP and CO-DRIFTS analysis, and a differential packed-bed reactor was used carry out the oxidation reaction; the effluent stream was analyzed using a GC to determine reaction kinetics. It was determined that CO binds most strongly to Pt, followed by Pd, and then Ni. The transition from single atom to sub-nanometer nanoparticles or nanoparticles shows a decrease in specific activity with increasing weight loading. At relatively larger weight loadings, for each metal, the order in CO transitions from above 1 to 0 (or slightly negative), while the order in O2 transitions from slightly negative or 0 to above 1. Pd, Pt, and Ni, at similar nominal weight loadings, have similar activities in different temperature ranges; this observation shows CO poisons the metal site but does not explain why at low weight loadings the order in CO increases above 1. Binding energies between metals and ceria as well as metal and CO may explain this observation. Bimetallic Pd/Pt catalysts seem to show apparent synergy due to the fact that the activation energy decreases well below the activation energy of monometallic systems of Pd and Pt.