Journal
CATALYSTS
Volume 11, Issue 1, Pages -Publisher
MDPI
DOI: 10.3390/catal11010116
Keywords
palladium; DRIFTS; modulated excitation; phase sensitive detection; baseline; oxidation state; quickEXAFS
Categories
Funding
- Competence Center for Materials Science and Technology (CCMX)
- Swiss National Science Foundation (SNF)
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Infrared spectroscopy is used to establish the oxidation state of metal-based catalysts. The baseline changes under alternate pulses of CO or H-2 and O-2 are proportional to the Pd content in Pd/Al2O3 samples. The reversible reduction-oxidation of Pd can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) under operando conditions.
Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H-2 and O-2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.
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