Abstract
Combined X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were applied to investigate the interaction between reaction atmosphere, adsorbates and Pt oxidation state of Pt/Al2O3 model diesel oxidation catalysts under CO/NO oxidation conditions. The Pt oxidation state was correlated to the adsorbates on the catalyst's surface. Even at low temperature the reaction atmosphere had a strong impact on the oxidation state of the catalyst, and the oxidation state in turn strongly affected CO adsorption on the Pt particles.
Highlights
Understanding catalysts at work is a key challenge for the rational design of new catalysts
During the first step the catalyst remained reduced: the XANES spectra did not change and the only visible peak in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra at 2096 cm-1 was attributed to CO adsorbed on reduced platinum [13, 14]
This change in oxidation state at low temperature is probably due to the oxidation of very small Pt particles, which are present in the sample prepared with the platinum acetylacetonate (PAA) precursor [5, 19]
Summary
Understanding catalysts at work is a key challenge for the rational design of new catalysts. After pre-reduction in 5 % H2/He (15mL/min) at 200 °C the catalyst was heated to 450 °C in He and background spectra for DRIFTS were acquired in 50 °C intervals during cooling to room temperature.
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