Submitted on August 4, 2008
Accepted on September 29, 2008
Reaction-Driven Restructuring of Rh-Pd and Pt-Pd Core-Shell Nanoparticles
Feng Tao 1, Michael E. Grass 1, Yawen Zhang 2, Derek R. Butcher 1, James R. Renzas 1, Zhi Liu 3, Jen Y. Chung 3, Bongjin S. Mun 3, Miquel Salmeron 4*, Gabor A. Somorjai 1*
1 Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.; Department of Chemistry, University of California, Berkeley CA 94720, USA.
2 Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.; Department of Chemistry, University of California, Berkeley CA 94720, USA.; College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
3 Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley CA 94720, USA.
4 Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.; Department of Materials Science and Engineering, University of California, Berkeley CA 94720, USA.
* To whom correspondence should be addressed.
Miquel Salmeron , E-mail: mbsalmeron{at}lbl.gov
Gabor A. Somorjai , E-mail: somorjai{at}berkeley.edu
Heterogeneous catalysts that contain bimetallic nanoparticles may undergo segregation of the metals driven by oxidizing and reducing environments. The structure and composition of core-shell Rh0.5Pd0.5 and Pt0.5Pd0.5 nanoparticle catalysts were studied in situ, during oxidizing, reducing, and catalytic reactions involving NO, O2, CO, and H2 using x-ray photoelectron spectroscopy in near ambient pressure. The Rh0.5Pd0.5 nanoparticles underwent dramatic and reversible changes in composition and chemical state in response to oxidizing or reducing conditions. In contrast, no significant segregation of Pd or Pt atoms was found in Pt0.5Pd0.5 nanoparticles. The distinct behavior in restructuring and chemical response of Rh0.5Pd0.5 and Pt0.5Pd0.5 nanoparticle catalysts under the same reaction conditions illustrates the flexibility and tunability of the structure of bimetallic nanoparticle catalysts during catalytic reactions.
