X-ray Photoelectron Spectroscopic Study of Reduced Alkali Tungsten Oxides with Localized and Delocalized Electrons

Abstract

In a series of Cs-doped tungsten oxides that underwent different degrees of reduction, new components and behaviors were found in X-ray photoelectron spectroscopy (XPS) signals of O−1s, W−4f, and Cs−3d and analyzed in terms of oxygen vacancies (V O s) and electron localization with the aid of first-principles calculations. Orthorhombic Cs 4 W 11 O 35 was reduced at high temperature to transform it to hexagonal tungsten bronze with increasing W 5+ trapped electrons, as detected in W−4f. The binding energy of W 5+ −4f showed a distinct redshift toward low saturation values that was implied to be due to W 5+ alignment on the hexagonal prismatic planes. The V O enthalpy of formation and the Bader charge calculated for each atom site supported this view, by identifying the preferred sites for V O and W 5+ on (020) in Cs 4 W 11 O 35 . The W 5+ component was newly admitted in O−1s at 531.25−531.94 eV and 532.35−533.04 eV, while the carbonation contributions were eliminated using C−1s deconvolution. In Cs−3d, a V O -related extra component was found on the high-energy side, which grew with increasing reduction time. These observations and calculations supported the proposition that electrons emitted from Cs should be delocalized, and those from V O s should be both localized and delocalized in Cs-doped tungsten oxides.

Hybrid bronzes: mixed-valence organic-inorganic metal oxides as a tunable material platform

“…Tungsten-based hybrid materials were fit in a similar manner, wherein doublets at 36.0 ± 0.5 eV (4f7/2) and 38.1 ± 0.5 eV (4f5/2), 34.7 ± 0.5 eV (4f7/2) and 36.9 ± 0.5 eV (4f5/2), and 33.3 ± 0.3 eV (4f7/2) and 35.4 ± 0.3 eV (4f5/2) correspond to W(VI), W(V), and W(IV), respectively. 42 We note that in the case of nominally unreduced W-based samples, some W 5+ is observed, consistent with previous reports of tungsten reduction induced by the combination of high vacuum and charge neutralization in the XPS chamber, 43 likely from creation of oxygen defects. Since the degree to which this effect occurs for already reduced tungstenbased oxide materials is not well-known, we incorporate the magnitude of this discrepancy as error in our calculated values of x in (L)zHxWO3 (Table 1).…”

Rational Cationic Disorder in Hexagonal Cesium Tungsten Bronze Nanoparticles for Infrared Absorption Materials

“…Orthorhombic Cs 4 W 11 O 35 contains periodically planar W defects on the prism plane in the hexagonal structure. 29,30 Therefore, the heat-induced transition was regarded as a topotactic reaction associated with the disappearance of planar W defects introduced by FSP with rapid quenching in a high oxidation atmosphere. 26 Simultaneously, W and Cs in Cs 0.33 WO 3 were uniformly distributed by atomic rearrangements.…”

“…Intermediate Cs 0.33 WO 3 NPs were synthesized by FSP with a loaded Cs/W ratio of 0.37 and then heated at 500 °C under 3% H 2 /Ar for 2 h. The XRD patterns in Figure a show the transition from a mixture of hexagonal Cs 0.33 WO 3 (ICDD:86–2578) and orthorhombic Cs 4 W 11 O 35 (ICDD:51–1891) to a single phase of hexagonal Cs 0.33 WO 3 following heat treatment. Orthorhombic Cs 4 W 11 O 35 contains periodically planar W defects on the prism plane in the hexagonal structure. , Therefore, the heat-induced transition was regarded as a topotactic reaction associated with the disappearance of planar W defects introduced by FSP with rapid quenching in a high oxidation atmosphere . Simultaneously, W and Cs in Cs 0.33 WO 3 were uniformly distributed by atomic rearrangements.…”

Effect of metal dopants on the electrochromic performance of hydrothermally-prepared tungsten oxide materials

“…The binding energy difference between these two doublets is set at 2.14 eV, maintaining the same full width at half maximum (FWHM) value, which is consistent with the literature. 30,31…”

“…The binding energy difference between these two doublets is set at 2.14 eV, maintaining the same full width at half maximum (FWHM) value, which is consistent with the literature. 30,31 The formation of low valence states (W 5+ ) is oen accompanied by the emergence of oxygen vacancies (V O ). 32 The formation of V O inside the structure is further conrmed by the O 1s core level which can deconvoluted into 2 main peaks (Fig.…”