Size Control of Pt Clusters on CeO2 Nanoparticles via an Incorporation–Segregation Mechanism and Study of Segregation Kinetics
journal contributionposted on 29.04.2016, 00:00 by Frank Pilger, Andrea Testino, Agnese Carino, Christian Proff, Anastasios Kambolis, Antonio Cervellino, Christian Ludwig
Recent literature on Pt/CeO2 catalysts reveals that ionic Pt species could be incorporated into the CeO2 lattice. Here we present a detailed study of Pt segregation in air and under a reducing atmosphere conducted on thermally treated samples by high-resolution X-ray diffraction (XRD) and X-ray absorption spectroscopy. We further perform a kinetic study by in situ XRD measurements with the aim of estimating the activation energy for Pt cluster segregation and coalescence in air, which was found to be ∼3.88 eV. This high activation energy indicates that Pt clusters are strongly anchored on the CeO2 surface and that their mobility is activated only at >900 °C. We clearly show the correlation between the nature of the segregated Pt particles and the applied thermal treatment for Pt/CeO2 nanomaterials prepared by the wet chemical route. On the basis of thorough characterization, we present a possible segregation pathway under oxidizing conditions as opposed to a mere surface reduction during a reducing treatment, leading to the coalescence of less anchored Pt. The catalytic performances confirm the remarkable activity and thermal stability of entities obtained via an incorporation–segregation mechanism.