Reversible formation of a PdCx phase in Pd nanoparticles upon CO and O2 exposure

Olivier Balmes; Andrea Resta; Didier Wermeille; Roberto Felici; Maria E. Messing; Knut Deppert; Zhi Liu; Michael E. Grass; Hendrik Bluhm; Richard van Rijn; Joost W. M. Frenken; Rasmus Westerström; Sara Blomberg; Johan Gustafson; Jesper N. Andersen; Edvin Lundgren

doi:10.1039/C2CP22873D

Reversible formation of a PdC_x phase in Pd nanoparticles upon CO and O₂ exposure†

Olivier Balmes,*^a Andrea Resta,^a Didier Wermeille,^a Roberto Felici,^a Maria E. Messing,^b Knut Deppert,^b Zhi Liu,^c Michael E. Grass,^c Hendrik Bluhm,^d Richard van Rijn,^e Joost W. M. Frenken,^e Rasmus Westerström,^f Sara Blomberg,^g Johan Gustafson,^g Jesper N. Andersen^g and Edvin Lundgren^g

Author affiliations

* Corresponding authors

^a ESRF, B. P. 220, F-38043 Grenoble, France
E-mail: balmes@esrf.fr

^b Solid State Physics, Lund University, Box 118, S-221 00 Lund, Sweden

^c ALS, Lawrence Berkeley National Laboratory, Berkeley, USA

^d Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, USA

^e Kammerlingh Onnes Laboratory, Leiden University, P. O. Box 9504, Leiden, The Netherlands

^f Surface Physics Group, University of Zürich, Winterthurerstr. 190, CH-8057 Zurich, Switzerland

^g Division of Synchrotron Radiation Research, Department of Physics, Lund University, Box 118, S-221 00 Lund, Sweden

Abstract

The structure and chemical composition of Pd nanoparticles exposed to pure CO and mixtures of CO and O₂ at elevated temperatures have been studied in situ by a combination of X-ray Diffraction and X-ray Photoelectron Spectroscopy in pressures ranging from ultra high vacuum to 10 mbar and from room temperature to a few hundred degrees celsius. Our investigation shows that under CO exposure, above a certain temperature, carbon dissolves into the Pd particles forming a carbide phase. Upon exposure to CO and O₂ mixtures, the carbide phase forms and disappears reversibly, switching at the stoichiometric ratio for CO oxidation. This finding opens new scenarios for the understanding of catalytic oxidation of C-based molecules.

Physical Chemistry Chemical Physics

Reversible formation of a PdC_x phase in Pd nanoparticles upon CO and O₂ exposure†

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Reversible formation of a PdC_x phase in Pd nanoparticles upon CO and O₂ exposure

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Physical Chemistry Chemical Physics