XANES study of hydrogen incorporation in a Pd-capped Nb thin film

Abstract

X-ray absorption near-edge structure ͑XANES͒ measurements were used to probe the H-charging-induced electronic structure changes of a 2400 Å Nb film capped with Pd. These results are discussed in terms of ab initio linear augmented plane-wave ͑LAPW͒ band-structure calculations for this material. The Pd-L 3 -edge XANES clearly manifested the spectral ͑Pd-d state related͒ changes expected for Pd-hydride formation, a white line feature degradation, and the appearance of a Pd-H antibonding feature at 6 eV above the threshold. The Nb-L 2,3 edge changes with H charging show a distinct enhancement of the white line strength; a feature 6 eV above the edges, associated with Nb-H antibonding states in analogy with the Pd results; the suppression of a threshold-onset feature of Nb metal; and a shift of the centrum of the white line feature towards the threshold. Comparison of the Nb sphere projection of the d 3/2 component of the LAPW density of states ͑DOS͒ to the Nb-L 2 -edge spectra yields good basic agreement with the observed spectral changes. In particular, the substantial theoretical reduction in the DOS at, and just above, the Fermi energy (E f ) is directly related to the near threshold Nb-L 2,3 spectral changes. The more modest white line enhancement in the theoretical DOS is noted and discussed. Nb-K-edge XANES are also discussed in terms of the Nb-site p-state projected LAPW DOS. This last comparison indicates a p-state reduction near E f upon H charging of the Nb.

Structural selectivity of supported Pd nanoparticles for catalytic NH3 oxidation resolved using combined operando spectroscopy

“…Palladium hydride gives rise to a distinct absorption feature at 3182 eV due to excitation of 2p electrons to a Pd-H antibonding state ( Figure 2). [29][30][31] The XANES spectrum of Pd/γ- Al2O3 collected under He at 100°C, after a reduction pretreatment ( Figure 2), is consistent with that of Pd foil for metallic Pd (0) oxidation state. After switching to the reactant (NH3/ O2) gas feed at 100°C, the Pd L3-edge XANES show increased intensity and broadening of the white line ( Figure 2) but without the characteristic absorption feature at 3182 eV for palladium hydride.…”

Revealing the Rapid Electrocatalytic Behavior of Ultrafine Amorphous Defective Nb2O5–x Nanocluster toward Superior Li–S Performance

“…36 Figure 3I shows the total electron yield (TEY) and fluorescence yield (FLY) spectra of A-Nb 2 O 5−x @MCS, the depressed peak intensity of FLY spectra could originate from the selfabsorption (the thickness effect) of the A-Nb 2 O 5−x nanocluster. 37 The first derivative XANES spectra are also shown in the Figure S14. Compared with FLY spectra, A-Nb 2 O 5−x @ MCS shows the lowest energy gap of 2.1 eV between A and B in TEY spectra with a narrow half-peak width.…”

“…However, A-Nb 2 O 5– x @MCS delivers the smallest energy gap of 2.3 eV and much dampened intensity of valley D, corresponding to the high distortion degree of octahedral symmetry Figure I shows the total electron yield (TEY) and fluorescence yield (FLY) spectra of A-Nb 2 O 5– x @MCS, the depressed peak intensity of FLY spectra could originate from the self-absorption (the thickness effect) of the A-Nb 2 O 5– x nanocluster . The first derivative XANES spectra are also shown in the Figure S14.…”

Probing the electronic and local structure of Sr$_{2-x}$La$_x$CoNbO$_6$ using near-edge and extended x-ray absorption fine structures

“…2(a, b) of [45]. Further, two prominent features 1 and 2, which are separated by ∼ 13 eV, can be attributed to the 1s →5p transition and the resonance due to multiple scattering of the photoelectrons from the neighboring atoms, respectively [46][47][48]. It is interesting to note that the intensity of the feature 2 remains almost invariant up to the x = 0.4 and then increases monotonically with further increase in the La substitution for the x 0.6 samples [see inset (a1) of Fig.…”