Homogeneous size-selected Pd and Pt nanoparticles (NP) supported on ZrO2 and ?-Al2O3 were synthesized by diblock copolymer encapsulation. The relation between their structure, chemical state, and catalytic activity was obtained via X-ray absorption fine-structure spectroscopy, X-ray photoelectron spectroscopy, and mass spectrometry.Prior to the onset of the NO reduction reaction with H2, NO-induced redispersion of Pd NPs over the ZrO2 support was observed, and Pdd+ species detected. This process parallels the high production of N2O at the onset of the reaction (>120�C), while at higher temperatures (= 150�C) the selectivity shifts toward N2. Concomitant with the onset of N2 production, the Pd atoms aggregate again into large metallic Pd NPs, which were found to constitute the active phase for the H2-reduction of NO. The evolution of the oxidation state of Pd and Pt NPs during the oxidation of NO and the role of the NP size will also be presented.

Evolution of the structure and chemical state of Pd and Pt nanoparticles during the in situ catalytic reduction and oxidation of NO

244th National Meeting (2012)

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