XPS Studies of the Initial Oxidation of Polycrystalline Rh Surface

Abstract

Increased interest in the oxidation process of polycrystalline rhodium, observed in recent years, is the result of its application in exhaust catalytic converters. However, most studies have involved sample surfaces with low Miller indices. In our research, we investigated polycrystalline rhodium foil containing crystallographically different, highly stepped, µm-sized crystallites. These crystallites were exposed to identical oxidizing conditions. To determine crystallographic orientation, the electron backscattering diffraction (EBSD) method was used. To investigate the initial stages of oxidation on the individual crystallites of Rh, X-ray photoelectron spectroscopy (XPS) studies were performed. The results obtained for the individual crystallites were compared and analyzed using chemical state quantification of XPS data and multivariate statistical analysis (MVA).

Highly efficient hydrogenation of furfural to valuable products catalysed by Rh (III), Pd (II), Ni (II), Fe (II) and Ru (II) half‐sandwich picolinamide and the SBA‐15 supported molecular complexes as pre‐catalysts

“…This observation is in agreement with the EDX analysis results. The XPS spectrum for C2@SBA‐15 exhibited two sets of doublets with binding energies of Rh 3d 5/2 at 309.4 eV and Rh 3d 3/2 at 313.3 eV, which confirmed the presence of Rh 3+ oxidation state species 53,54 …”

“…The XPS spectrum for C2@SBA-15 exhibited two sets of doublets with binding energies of Rh 3d 5/2 at 309.4 eV and Rh 3d 3/2 at 313.3 eV, which confirmed the presence of Rh 3+ oxidation state species. 53,54 The Ni 2p XPS spectrum for C3@SBA-15 showed Ni 2p 3/2 (856.3 eV), Ni 2p 3/2 satellite (862.2 eV), Ni 2p 1/2 (874.2 eV), and Ni 2p 1/2 satellite (882.5 eV) which were attributed to Ni 2+ metal centre. These binding energies are consistent with reported literature values for nickelcontaining compounds.…”

A Polycrystalline Pd Surface Studied by Two-Dimensional Surface Optical Reflectance during CO Oxidation: Bridging the Materials Gap

“…These crystals, which consist of a large number of randomly oriented grains, will, when polished, exhibit a wide variety of surface orientations. Therefore, an increasing number of studies have been performed in which two-dimensional (2D) techniques are used to study polycrystalline samples. − With appropriate 2D resolution, these polycrystals now act as a collection of a vast number of separate single crystals, all within one sample . In this way, multiple surface orientations can be measured simultaneously, which is much more efficient and also makes it easier to compare results, as we can expect similar experimental conditions between neighboring grains.…”