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Surface Segregation of Pd from TiO 2 ‐Supported AuPd Nanoalloys under CO Oxidation Conditions Observed In situ by ETEM and DRIFTS
Author(s) -
Delannoy Laurent,
Giorgio Suzanne,
Mattei Jean Gabriel,
Henry Claude R.,
El Kolli Nadia,
Méthivier Christophe,
Louis Catherine
Publication year - 2013
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200618
Subject(s) - bimetallic strip , x ray photoelectron spectroscopy , catalysis , nanoparticle , diffuse reflectance infrared fourier transform , materials science , high resolution transmission electron microscopy , fourier transform infrared spectroscopy , palladium , chemical engineering , precipitation , chemistry , photocatalysis , transmission electron microscopy , nanotechnology , organic chemistry , physics , meteorology , engineering
A TiO 2 ‐supported AuPd bimetallic catalyst with an Au/Pd atomic ratio of 8 was prepared by deposition‐precipitation with urea, and its activity in CO oxidation at room temperature was compared to the one of a monometallic Au/TiO 2 catalyst. X‐ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses suggest that Au‐Pd/TiO 2 contains bimetallic nanoparticles after reduction under H 2 at 500 °C although the presence of monometallic Au particles cannot be totally excluded. The evolution of the AuPd nanoparticles surface composition during exposure to O 2 and CO/O 2 was studied in situ by environmental high resolution electron microscopy (ETEM) and DRIFTS. Pd segregation at the surface of the bimetallic nanoparticles was evidenced by DRIFTS and directly observed by ETEM under O 2 and CO/O 2 with the formation of Au core ‐Pd shell structure. The changes in the surface composition of the Au‐Pd nanoparticles under CO/O 2 was paralleled with the higher rate of deactivation in the first reaction stages observed for Au‐Pd/TiO 2 compared to Au/TiO 2 , which could be related to the possible replacement of Au in low coordination sites, at the origin of the high activity in CO oxidation, by Pd atoms. These results noticeably underline the modifications induced by the reactant that can undergo a bimetallic AuPd catalyst.