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Dynamic “operando” observation of 1 wt% Pd-based TWCs: Simultaneous XAS/DRIFTS/mass spectrometry analysis of the effects of Ce0.5Zr0.5O2loading on structure, reactivity and performance

Authors
Journal
Catalysis Today
0920-5861
Publisher
Elsevier
Publication Date
Volume
145
Identifiers
DOI: 10.1016/j.cattod.2008.09.029
Keywords
  • Pd-Based Twcs
  • Ceo2–Zro2
  • Al2O3
  • Operando And In Situ Measurements
  • Xanes
  • Energy Dispersive Exafs
  • Drifts
  • Mass Spectrometry
Disciplines
  • Chemistry
  • Physics

Abstract

Abstract The behavior of 1 wt% Pd-TWCs (three-way catalysts), containing up to 33 wt% Ce 0.5Zr 0.5O 2 is followed under reducing (CO) and oxidizing (NO) cycling conditions. The dynamic behavior of these systems is analyzed using a synchronous, time-resolved energy dispersive X-ray absorption spectroscopy (XAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) set-up with subsecond time resolution. Two main physico-chemical phenomena corresponding to noble metal morphological (size/shape) changes and the redox behavior of the noble metal–promoter interface are shown to control the TWC response to NO/CO cycling conditions. Metal-only aspects strongly influence N–O dissociation and N–N coupling steps while the metal–promoter interface has a global influence on both N 2 and CO 2 formation via oxygen handling (storage/release) properties. The relative importance of these two phenomena is studied as a function of the Ce 0.5Zr 0.5O 2 promoter content of the catalysts.

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