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Revealing the Dynamic Structure of Complex Solid Catalysts Using Modulated Excitation X‐ray Diffraction
Author(s) -
Ferri Davide,
Newton Mark A.,
Di Michiel Marco,
Chiarello Gian Luca,
Yoon Songhak,
Lu Ye,
Andrieux Jérôme
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201403094
Subject(s) - cerium , extended x ray absorption fine structure , diffuse reflectance infrared fourier transform , catalysis , context (archaeology) , redox , cerium oxide , diffuse reflection , diffraction , materials science , fourier transform infrared spectroscopy , adsorption , palladium , analytical chemistry (journal) , absorption (acoustics) , spectroscopy , x ray crystallography , chemistry , absorption spectroscopy , inorganic chemistry , optics , photocatalysis , physics , paleontology , biochemistry , chromatography , quantum mechanics , composite material , biology
X‐ray diffraction (XRD) is typically silent towards information on low loadings of precious metals on solid catalysts because of their finely dispersed nature. When combined with a concentration modulation approach, time‐resolved high‐energy XRD is able to provide the detailed redox dynamics of palladium nanoparticles with a diameter of 2 nm in 2 wt % Pd/CZ (CZ=ceria–zirconia), which is a difficult sample for extended X‐ray absorption fine structure (EXAFS) measurements because of the cerium component. The temporal evolution of the Pd(111) and Ce(111) reflections together with surface information from synchronous diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements reveals that Ce maintains Pd oxidized in the CO pulse, whereas reduction is detected at the beginning of the O 2 pulse. Oxygen is likely transferred from Pd to Ce 3+ before the onset of Pd re‐oxidation. In this context, adsorbed carbonates appear to be the rate‐limiting species for re‐oxidation.