Role of Small Pd Ensembles in Boosting CO Oxidation in AuPd Alloys.
We present a theoretical explanation on how PdAu alloy catalysts can enhance the oxidation of CO molecules based on density functional theory calculations of CO adsorption and oxidation on AuPd/Pd(111) surfaces. Our study suggests that the enhanced activity is largely attributed to the possible existence of "partially-poisoned" Pd ensembles that accommodate fewer CO molecules than Pd atoms. Whereas the oxidation of preadsorbed CO is likely governed by O2 trapping, our study shows that small Pd ensembles such as dimers and compact trimers tend to provide more active sites than larger ensembles; CO adsorbed on a Pd monomer is found to react hardly with O2 to form CO2. In addition, we find the tendency of CO-induced Pd agglomeration, which may in turn facilitate CO oxidation by creating more dimers and compact trimers as compared with the adsorbate-free surface where monomers are likely prevailing.
†Department of Chemical Engineering, The University of Texas at Austin, Texas 78712, United States.
Hyung Chul
HC
Ham
†Department of Chemical Engineering, The University of Texas at Austin, Texas 78712, United States.
J Adam
JA
Stephens
†Department of Chemical Engineering, The University of Texas at Austin, Texas 78712, United States.
Gyeong S
GS
Hwang
‡Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), Seoul, Korea.
Jonghee
J
Han
‡Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), Seoul, Korea.
Suk Woo
SW
Nam
‡Fuel Cell Research Center, Korea Institute of Science and Technology (KIST), Seoul, Korea.
Tae Hoon
TH
Lim
CO oxidation; palladium−gold alloys; surface ensembles