A transient in situ FTIR and XANES study of CO oxidation over Pt/Al2O3 catalysts
Artikel i vetenskaplig tidskrift, 2004

We report experimental results for the oxidation of CO over supported Pt/Al2O3 catalysts operating in oxygen excess at atmospheric pressure. To study the reaction kinetics under transient conditions we have employed step changes of the O2 concentration by intermittently switching off the O2 supply at various temperatures ranging from 523 to 623 K. Detailed in situ FTIR and XANES data for CO coverage and the chemical state of Pt, respectively, are presented together with the CO conversion, which in both cases was monitored by mass spectrometry. A red-shift of the vibrational frequency of linearly bonded CO which correlates with a blue-shift of the Pt LIII binding energy indicates that the Pt catalyst initially is partially oxidised and gradually reduced when the O2 supply is switched off. Control experiments with a NO2 oxidised Pt/Al2O3 catalyst support these findings. A hysteresis in the catalytic activity due to the different rates whereby Pt is oxidised and reduced as a function of gas-phase composition is observed. The activation energy for the Pt oxide reduction (decomposition) process is estimated to be about 50 kJ/mol. The results further emphasise that the conventional three-step Langmuir-Hinshelwood (LH) scheme used to interpret CO oxidation on Pt surfaces must be complemented by a Pt oxidation and reduction mechanism during transient conditions. Moreover, FTIR data suggest that during the extinction, the partially oxidised platinum surface is reduced by chemisorbed CO which should be explicitly accounted for in the modeling of the reaction mechanism.

Ignition

Platinum

Step-response experiments

Pt/Al<sub>2</sub>O<sub>3</sub>

XANES

FTIR

Catalysis

CO oxidation

Extinction

Platinum oxide

Författare

Per-Anders Carlsson

Kompetenscentrum katalys (KCK)

Chalmers, Institutionen för kemiteknik och miljövetenskap

Lars Österlund

Kompetenscentrum katalys (KCK)

Chalmers, Teknisk fysik

Peter Thormählen

Chalmers, Teknisk fysik, Kemisk fysik

Kompetenscentrum katalys (KCK)

Anders Palmqvist

Kompetenscentrum katalys (KCK)

Chalmers, Institutionen för material- och ytkemi, Teknisk ytkemi

Erik Fridell

Chalmers, Teknisk fysik, Kemisk fysik

Kompetenscentrum katalys (KCK)

Jonas Jansson

Chalmers, Institutionen för kemiteknik och miljövetenskap

Kompetenscentrum katalys (KCK)

Magnus Skoglundh

Chalmers, Institutionen för material- och ytkemi, Teknisk ytkemi

Kompetenscentrum katalys (KCK)

Journal of Catalysis

0021-9517 (ISSN) 1090-2694 (eISSN)

Vol. 226 422-434

Drivkrafter

Hållbar utveckling

Styrkeområden

Nanovetenskap och nanoteknik

Transport

Energi

Materialvetenskap

Ämneskategorier

Fysik

Miljövetenskap

DOI

10.1016/j.jcat.2004.06.009