In situ XAS and XRD investigations during reactivation of ceria based NO x storage reduction catalysts M. Casapu 1 , S. Hannemann 1 , J.-D. Grunwaldt 1 , M. Maciejewski 1 , A. Baiker 1 , E. Welter 2 , S. Eckhoff 3 , U. Göbel 3 2 Department of Chemistry and Apllied Biosciences, ETH Zurich, Hönggerberg – HCI, CH-8093 Zürich 2 HASYLAB at DESY, Notkestrasse 85, D-22607 Hamburg 3 Umicore AG & Co. KG, Rodenbacher Chaussee 4, D-63403 Hanau-Wolfgang Lean-burn engines with direct fuel injection have been recently introduced in car industry to decrease fuel consumption [1]. However, the well-known three-way catalyst cannot be used for efficient NO x -removal due to an excess of air. Therefore new catalyst concepts for NO x -removal have been developed. Among them, the NO x -storage-reduction (NSR) catalyst system is well established [2]. Under operating conditions some deterioration is usually observed because of poisoning by sulfur and thermal deterioration leading to formation of mixed oxides such as aluminates, cerates, and zirconates through reactions of the NO x storage component material with the support material or other washcoat compounds [3]. Recently, we have found that the BaCeO 3 formed in a thermally aged Pt-Ba-CeO 2 catalyst can be decomposed under certain process conditions, e.g. in the presence of NO 2 , H 2 O and CO 2 [4]. In order to further understand this reactivation process, both information on amorphous (short-range order) and crystalline (long range order) species are required. A combination of XAS and XRD is therefore required, which was built at beamline X1. Here we describe briefly the experimental setup used and report on some of the data recorded. The combination of XAS and XRD is not new and has been applied previously at beamline X1 [5,6]. The setup is based on the system, assembled by J. Wienold [6]. In Fig. 1, the experimental setup is shown schematically, it had has been built up in 2005 and was improved during a beamtime in 2006. The XRD patterns were taken using a MAR345 area detector (impage plate). As in situ cell either a capiallary or, as depicted here a heat-/colleable cell with Kapton-windows was used. In this case also fluorescence EXAFS data could be recorded by tilting the sample holder to a 45° position and using a 7-element Si(Li)-detector (Gresham). Transmission EXAFS data were taken in two different ways: Either by installing a second ionization chamber between the sample and the beamstop or by using a pin-diode with appropriate shielding in front of the beamstop. The latter arrangement allowed us that both EXAFS and XRD measurements could be taken in parallel. Nevertheless, it has to be noted that the image plate had to be read out after illumination so that placing the ionization chamber into the beam was not time limiting. Figure 2 shows spectra taken on an aged 0.75%Pt-16%Ba-CeO 2 sample that contained significant amounts of BaCeO 3 . The spectrum at the Pt L 3 -edge was taken in fluorescence mode, at the Ba K-edge the pin diode was applied and the XRD patterns were taken below the Ba K-edge at 0.332 Å (37.4 keV). Fig. 1: Experimental setup for combined EXAFS/ XRD measurements. 1391