Numerical Simulation of the Platinum L_III Edge White Line Relative to Nanometer Scale Clusters

Abstract

From an experimental point of view and more particularly in heterogeneous catalysis, the LIII white line is at the center of electronic charge transfer either between either the nanometer scale metallic particle and the support or between the two metals which are present inside the cluster. In this work, we show that a strong correlation exists between the intensity of the white line and the size of the cluster. Thus, at least two physical phenomenon can affect the intensity of the white line: the size of the cluster, which can be considered as an intrinsic effect (density of state of nanometer scale platinum cluster are far from the bulk one), and a possible charge transfer between the cluster and the support, which can be considered as an extrinsic one. If the first results obtained with the FeFF program are encouraging, it is clear that to go further in the analysis, the detailed geometric configurations present in the cluster surface have to be integrated very precisely in order to obtain quantitative effects that would be more clearly related to the characteristics of the density of states.

Structure and Size of Bimetallic Palladium-Platinum Clusters in an Hydrotreatment

“…After in situ treatment under H 2 , the platinum atoms are reduced to metallic state as indicated by the similarity in the intensity of the white line of the Pt foil to that of the catalyst [40][41]. Moreover, a comparison of the EXAFS part of the absorption spectra for Pd 6 Pt catalyst (Fig.…”

Effect of the impregnation order on the nature of metal particles of bi-functional Pt/Pd-supported zeolite Beta materials and on their catalytic activity for the hydroisomerization of alkanes

“…Since the Pt data were recorded at the L III -edge, the 2p 3/2 -5d 3/2 /5d 5/2 transitions are dipole allowed and therefore the variations in the rising absorption edge are likely to reflect changes in the 6p-5d hybridization and final d-state electron density caused by the probable presence of oxygen in the Pt/Beta sample and an 'alloying interaction' with Pd for the bi-metallic species [59]. Alternatively, it may reflect a difference in the Pt cluster shape [60,61]. In order to determine further the types of species present in the zeolite samples, EXAFS analysis was performed.…”

Time Resolved Operando X-ray Techniques in Catalysis, a Case Study: CO Oxidation by O2 over Pt Surfaces and Alumina Supported Pt Catalysts

“…The Pt L3-edge during these experiments shows two subtle, but measurable, changes during these transient experiments: variation in the intensity of the Pt L3-edge white line and the energetic position of the edge itself (0.6 eV at most). The overall shape of the Pt XANES is undeniably metallic and these changes are indicative, within certain approximations-as the detailed structure of the Pt L3-edge XANES can also be indicative of changes in size [108][109][110], or indeed morphology [111]-of the oxidation of the surfaces of nanoparticles during the switch from a new reducing (CO) to net oxidizing (O2) environment.…”