A Study of Nanophase Tungsten Oxides Thin Films by XPS

Barreca, Davide; Carta, Giovanni; Gasparotto, Alberto; Rossetto, G.; Tondello, Eugenio; Zanella, P.

doi:10.1116/11.20020801

Cited by 54 publications

(55 citation statements)

References 10 publications

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“…For WO 3 the spectrum is deconvoluted in two peaks with weight ratio 4:3, nearly equal width of 1.7 eV, and binding energies of 36.1 ± 0.1 eV for W 4 f 7/2 and 38.2 ± 0.1 eV for W 4 f 5/2 . The positions and shapes of these peaks agree with W in oxidation state +6, as expected for stoichiometric WO 3 2122. For WO 3− x and H z WO 3− x the W 4 f signal is broadened towards lower energy, reflecting the appearance of a new oxidation state lower than +6.…”

Section: Resultssupporting

confidence: 75%

Intrinsic Defects and H Doping in WO3

Zhu

Vasilopoulou

Davazoglou

et al. 2017

Sci Rep

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WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy.

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Section: Resultssupporting

confidence: 75%

Intrinsic Defects and H Doping in WO3

Zhu

Vasilopoulou

Davazoglou

et al. 2017

Sci Rep

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“…The spectrum exhibits two peaks at 232.3 eV (Mo 3d 3/2 ) and 235.4 eV (Mo 3d 5/2 ), confirming the presence of PMo 12 in the PMo 12 @PPy sample, which is in the Mo VI oxidation state . The core‐level W 4f spectrum shows two peaks at 37.54 eV (W 4f 5/2 ) and 35.4 eV (W 4f 7/2 ) with spin‐orbit splitting of 2.14 eV as shown in Figure d. It is further confirmed that the W atoms in PW 12 in PW 12 @PPy exhibit an oxidation state of W VI …”

Section: Resultssupporting

confidence: 79%

“…[32] The core-level W4fs pectrum shows two peaks at 37.54 eV (W 4f 5/2 )a nd 35.4 eV (W 4f 7/2 )w iths pin-orbit splitting of 2.14 eV as shown in Figure 3d.I ti sf urtherc onfirmed that the W atoms in PW 12 in PW 12 @PPy exhibit an oxidation state of W VI . [33,34] High surface and 1D hollow nanostructures are ideally suited for energy-storage devices.B ET analyses of PMo 12 @PPy and PW 12 @PPy samples were carriedo ut and the results are presented in Figure 4. BET surfacea reas for PPy-Npipes, PMo 12 @PPy,a nd PW 12 @PPy samples were found to be 43.11, 36.47, and 34.14 m 2 g À1 ,r espectively.T his decrease in the BET surfacea reas for PMo 12 @PPy and PW 12 @PPy is attributed to the inclusion of the PMo 12 and PW 12 nanoparticles because of their heavy contribution in the hybrid nanocomposites.…”

Section: Resultsmentioning

confidence: 99%

Functionalization of Polypyrrole Nanopipes with Redox‐Active Polyoxometalates for High Energy Density Supercapacitors

et al. 2017

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Hybrid materials are very attractive for the fabrication of high‐performance supercapacitors. Here, we have explored organic–inorganic hybrid materials based on open‐end porous 1 D polypyrrole nanopipes (PPy‐NPipes) and heteropolyoxometalates (phosphotungstate ([PW12O40]3−, PW12) or phosphomolybdate ([PMo12O40]3−, PMo12)) that display excellent areal capacitances. Two different hybrid materials (PMo12@PPy and PW12@PPy) were effectively synthesized and used for symmetric supercapacitors. The anchoring of the inorganic nanoclusters onto the conducting polymer nanopipes led to electrodes that stood up to our best expectations exhibiting outstanding areal capacitances that are almost 1.5 to 2 fold higher than that of pristine PPy‐NPipes. In addition, symmetric cells based on PMo12@PPy and PW12@PPy hybrid electrodes were fabricated and showed significant improvement in cell performance with very high volumetric capacitances in the range of 6.3–6.8 F cm−3 (considering the volume of whole device). Indeed, they provide extended potential windows in acidic electrolytes (up to 1.5 V) which led to ultrahigh energy densities of 1.5 and 2.2 mWh cm−3 for PMo12@PPy and PW12@PPy cells, respectively. Thus, these unique organic‐inorganic hybrid symmetric cells displayed extraordinary electrochemical performances far exceeding those of more complex asymmetric systems.

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“…The binding energy of W 4f 7/2 and W 4f 5/2 is located at 35.8 ± 0.05 and 37.9 ± 0.05 eV (with a peak ratio of 4:3), respectively. The position and the shape of these peaks are representative of W VI oxidation state . In addition, there are two evident peaks at lower binding energy of W 4f 7/2 = 34.9 eV and W 4f 5/2 = 37.0 eV (with a peak ratio of 4:3) in all the figures except Figure h, which are associated with the reduction state (W V ) ions on the film surface, indicating that these POMs films are reduced by Al to form HPBs films .…”

Section: Resultsmentioning

confidence: 88%

A Strategy to Obtain Long‐Term Stable Heteropoly Blues for Photosensitive Property Investigations

Chen

et al. 2018

Advanced Optical Materials

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which should have wide spectrum absorptions, anchoring groups, and appropriate energy levels in order to absorb more sunlight and excite the ground-state electrons to the excited state, then inject into the semiconductor conduction band, while the holes remain in the dye molecule form the charge separations, which ensure the effective regenerations of the photosensitizers and the unidirectional electron injections. [2] In recent decades, great efforts have been made to develop the photosensitizers with high stability, low-cost, and high solar energy conversion in the fields of photocatalysts and solar cells. [3,4] However, developing broad-spectrum photosensitizers is still a big challenge. At present, the commonly used photosensitizers including ruthenium-pyridine, porphyrin, and pure organic dyes, have efficiently improved the power conversion efficiencies (PCEs) of the DSSCs. [5] However, their large-scale productions and applications in photovoltaic industry have been limited by their high costs and the cumbersome process in the synthesis and purification of photosensitizers. [6] Furthermore, the defects of some photosensitizers in spectral absorption also restrict the utilization of sunlight. So, it is urgent to develop the photosensitizers with environment-friendly, simple preparations, low costs, and wide spectra absorptions.Heteropoly blues (HPBs) is a reductive state of polyoxometalates (POMs representing oxidation state) with fascinating structures, abundant element compositions, reversible redox properties, and wide pH stability. [7,8] The advantages of HPBs as photosensitizer are as follows: i) their wide and strong spectral absorptions in visible and near-IR regions; ii) the anchoring groups are easily to coordinated to HPBs to firmly adsorb on the semiconductor surface; iii) their energy levels involving the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) can be adjusted by the composition, structure, and charge density to ensure the effective unidirectional electron injections and photosensitizer regenerations; [9] iv) their excellent light, thermal and electrochemical stability, their ability to accept or lose "blue" electrons without any structural transformations. As a kind of the potential photosensitizer candidates, HPBs have been increasingly recognized in terms of photocatalysis and solar cells. [10][11][12][13][14] However, the instability of HPBs in the air restricts the further research of their photosensitivity and their use as the photosensitizers in DSSCs.The photosensitizer is the soul of dye-sensitized solar cells (DSSCs), i.e., the key factor influencing the performance of DSSCs. The commonly used photo sensitizers are expensive carboxylic pyridine ruthenium-based complexes, so it is urgent to develop low-cost photosensitizers. Heteropoly blues (HPBs) could be a kind of excellent photosensitizers due to their wide spectra absorption; however, most of them are hardly stable in the air. Here, a strategy of combining the improved vacuum...

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A Study of Nanophase Tungsten Oxides Thin Films by XPS

Cited by 54 publications

References 10 publications

Intrinsic Defects and H Doping in WO3

Intrinsic Defects and H Doping in WO3

Functionalization of Polypyrrole Nanopipes with Redox‐Active Polyoxometalates for High Energy Density Supercapacitors

A Strategy to Obtain Long‐Term Stable Heteropoly Blues for Photosensitive Property Investigations

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