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Characterization of Surface Structure and Oxidation/Reduction Behaviour of Pd-Pt/Al2O3 Model Catalysts

Natalia Martin (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Johan Nilsson (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Magnus Skoglundh (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Emma Adams (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Xueting Wang (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Peter Velin (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi) ; Gudmund Smedler ; Agnes Rai ; David Thompsett ; Hidde Brongersma ; Thomas Grehl ; Giovanni Agostini ; Olivier Mathon ; Stefan Carlson ; Katarina Norén ; Francisco Javier Martinez-Casado ; Zdenek Matej ; Olivier Balmes ; Per-Anders Carlsson (Kompetenscentrum katalys (KCK) ; Institutionen för kemi och kemiteknik, Teknisk ytkemi)
Journal of Physical Chemistry C (1932-7447). Vol. 120 (2016), p. 28009-28020.
[Artikel, refereegranskad vetenskaplig]

Structural and morphological characterisation of bimetallic Pd-Pt/Al2O3 model cat- alysts are performed using X-ray diffraction, X-ray absorption spectroscopy, transmis- sion electron microscopy and CO chemisorption. Further, the catalysts were studied under oxidising and reducing conditions using both X-ray absorption spectroscopy and low-energy ion scattering spectroscopy. For the as-prepared catalysts, the existence of alloyed bimetallic Pd-Pt particles and of (tetragonal) PdO were found for the samples calcined at 800 �C. PdO is present in form of crystals at the surface of the Pd-Pt par- ticles or as isolated PdO crystals on the support oxide. Bimetallic Pd-Pt nanoparticles were only formed on the Pd-Pt catalysts after calcination at 800 �C. The results show that the Pd-Pt nanoparticles undergo reversible changes in surface structure composi- tion and chemical state in response to oxidising or reducing conditions. Under oxidising conditions Pd segregates to the shell and oxidises forming PdO, while under reducing conditions regions with metallic Pd and Pd-Pt alloys were observed at the surface. No bimetallic Pd-Pt nanoparticles were observed for the sample initially calcined at 500 �C, but instead isolated monometallic particles, where small Pt particles are easily oxidised under O2 treatment. In the monometallic catalysts, the Pd is found to be com- pletely oxidised already after calcination and to consist of metallic Pd after reductive treatment.



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Denna post skapades 2016-11-11. Senast ändrad 2017-01-23.
CPL Pubid: 245036