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XANES
About: XANES is a research topic. Over the lifetime, 7737 publications have been published within this topic receiving 188032 citations.
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68 citations
TL;DR: In this paper, a detailed discussion of the enhancement of the O 2 reduction kinetics based on the physical and electronic properties of the catalysts is presented, and the characterization techniques considered were high-resolution transmission electron microscopy, XRD (X-ray diffraction), in situ XANES (Xray absorption near edge structure), and EXAFS (extended X-ray absorption fine structure) measurements.
Abstract: The oxygen reduction reaction (ORR) was studied on carbon-dispersed Pt 3 Co, PtCo, and Pt 3 Ni alloys in KOH electrolyte. A detailed discussion of the enhancement of the O 2 reduction kinetics based on the physical and electronic properties of the catalysts is presented. The characterization techniques considered were high-resolution transmission electron microscopy, XRD (X-ray diffraction), in situ XANES (X-ray absorption near edge structure), and EXAFS (extended X-ray absorption fine structure) measurements. Cyclic voltammetry and steady-state polarization measurements for the ORR were conducted using a rotating ring-disk electrode. The XANES results at the Pt L 3 edge at anodic potentials showed lower oxide coverage on the PtCo/C catalysts, while at the Co and Ni K edges the results evidenced compositions that include Co or Ni metals and oxides. The XRD and EXAFS analyses showed a slight reduction of the Pt-Pt interatomic distance in the Pt alloys compared to Pt/C. The polarization curves indicated that the 4-electron mechanism is mainly followed for the ORR on all materials. The highest electrocatalytic activity was obtained for the PtCo/C alloy (1:1 atomic ratio), and this was attributed to less Pt-OH formation or faster Pt-O - electroreduction due to a lower Pt d-band center.
68 citations
TL;DR: In this paper, the x-ray absorption near-edge structure (XANES) at the K edge of the diluted magnetic semiconductor (Ga,Mn) was calculated using the linearized augmented plane wave method.
Abstract: The band structure of the diluted magnetic semiconductor (Ga,Mn)N, and the x-ray absorption near-edge structure (XANES) at the K edge of Mn, were calculated using the linearized augmented plane wave method. The calculated K-edge spectra fit well with experimental data obtained on samples of Ga1-xMnxN with a wide range of Mn content, from x=0.3% to 5.7%. These samples were grown by molecular beam epitaxy. X-ray diffraction measurements and extended x-ray absorption fine structure studies were used to confirm the wurtzite structure of the samples, the absence of any secondary phase, and the substitutional position of Mn in the gallium sublattice of GaN. The shape of the measured XANES spectra does not depend on the Mn content, implying the same valence state and local atomic structure around the Mn atom in all samples. The comparison between the measured spectra and the results of the ab initio calculation offers a clear interpretation of the preedge structure: It is mainly due to dipolar transitions, with a single peak in the case of Mn2+ and an additional peak for Mn3+. Such a behavior of the XANES preedge of Mn2+ was confirmed experimentally on Ga,MnAs and Zn,MnTe. We conclude that the valence state of Mn in wurtzite (Ga,Mn)N is 3+, a conclusion which is also supported by infrared optical transmission and magnetization data obtained on the same samples.
68 citations
TL;DR: This Article shows that the detailed molecular packing in thin organic semiconductor films can be solved through a combination of grazing incidence X-ray diffraction (GIXD), near-edgeX-ray absorption spectra fine structure (NEXAFS) spectroscopy, energy minimization packing calculations, and structure refinement of the diffraction data.
Abstract: Understanding the structure−property relationship for organic semiconductors is crucial in rational molecular design and organic thin film process control. Charge carrier transport in organic field-effect transistors predominantly occurs in a few semiconductor layers close to the interface in contact with the dielectric layer, and the transport properties depend sensitively on the precise molecular packing. Therefore, a better understanding of the impact of molecular packing and thin film morphology in the first few monolayers above the dielectric layer on charge transport is needed to improve the transistor performance. In this Article, we show that the detailed molecular packing in thin organic semiconductor films can be solved through a combination of grazing incidence X-ray diffraction (GIXD), near-edge X-ray absorption spectra fine structure (NEXAFS) spectroscopy, energy minimization packing calculations, and structure refinement of the diffraction data. We solve the thin film structure for 2 and 20 ...
68 citations
TL;DR: In this article, a carbon and nitrogen self-doped TiO 2 hollow spheres (CNTH) with oxygen vacancies and Ti3+ were synthesized by a one-pot hydrothermal strategy in H2O C2H5OH HF H 2O2 mixed solution with TiCN as a precursor of anatase TiO2 and selfdoping source of N and C. The resulting CNTH photocatalyst showed enhanced visible-light photocatalytic activity for H2 production.
67 citations