Photoelectrochemical Properties of Nanostructured Tungsten Trioxide Films

Santato, Clara; Ulmann, and Martine; Augustyński, Jan

doi:10.1021/jp002232q

Cited by 477 publications

(381 citation statements)

References 26 publications

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“…29 CV data were collected at a scan rate of 5 mV/s within a potential window between +0.2 and -0.6 V ( Figure 10A). A cathodic peak at -0.4 V and an anodic peak at -0.2 V were observed with and without UV light exposure ( Figure 10A).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

et al. 2006

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Metal oxide nanostructures hold great potential for photovoltaic (PV), photoelectrochemical (PEC), and photocatalytic applications. Whereas thin films of various materials of both nanoparticle and nanorod morphologies have been widely investigated, there have been few inquiries into nanodisk structures. Here, we report the synthesis of ultrathin WO 3 nanodisks using a wet chemical route with poly(ethylene glycol) (PEG) as a surface modulator. The reported nanodisk structure is based on the interaction of the nonionic 10000 g/mol PEG molecules with tungsten oxoanion precursors. The WO 3 nanostructures formed are dominated by very thin disks with dimensions on the nanometer to micrometer scale. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal the structures to have dimensions on the order of 350-1000 nm in length, 200-750 nm in width, and 7-18 nm in thickness and possessing textured single-crystalline features. A number of analytical techniques were used to characterize the WO 3 nanodisks, including selected-area electron diffraction (SAED), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Raman scattering spectroscopy, UV-visible spectrophotometry, and cyclic voltammetry (CV). The growth of the WO 3 nanodisks was inhibited in the [010] crystal direction, leading to ultrathin morphologies in the monoclinic crystal phase. The large flat surface area and high aspect ratio of the WO 3 nanodisks are potentially useful in PEC cells for hydrogen production via direct water splitting, as has been demonstrated in a preliminary experiment with external bias.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

et al. 2006

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“…20,28 According to a computational study, 29 the hydroxyl radical is stabilized on WO 3 surfaces, and the catalytic cycle for O 2 (g) evolution is thermodynamically viable at a potential of $2.3 V vs. NHE. Most experimental studies have assumed that either eqn (1) or (2) is responsible for current flow at WO 3 photoanodes in neutral and acidic solutions, as long as the electrolyte is thermodynamically more stable than water at the same pH value.…”

Section: Broader Contextmentioning

confidence: 99%

A quantitative assessment of the competition between water and anion oxidation at WO3 photoanodes in acidic aqueous electrolytes

Zhanaidarova

Brunschwig

et al. 2012

Energy Environ. Sci.

285

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The faradaic efficiency for O 2 (g) evolution at thin-film WO 3 photoanodes has been evaluated in a series of acidic aqueous electrolytes. In 1.0 M H 2 SO 4 , persulfate was the predominant photoelectrochemical oxidation product, and no O 2 was detected unless catalytic quantities of Ag + (aq) were added to the electrolyte. In contact with 1.0 M HClO 4 , dissolved O 2 was observed with nearly unity faradaic efficiency, but addition of a hole scavenger, 4-cyanopyridine N-oxide, completely suppressed O 2 formation. In 1.0 M HCl, Cl 2 (g) was the primary oxidation product. These results indicate that at WO 3 photoanodes, water oxidation is dominated by oxidation of the acid anions in 1.0 M HCl, H 2 SO 4 , and HClO 4 , respectively.

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“…5,6 The deposition of WO 3 •H 2 O was performed using a newly developed solvothermal method. A solution of 2 mmol WCl 6 in 70 mL ethanol was prepared in a globe box filled with dry air to avoid hydrolysis of WCl 6 by atmospheric humidity.…”

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confidence: 99%

“…A solution of 2 mmol WCl 6 in 70 mL ethanol was prepared in a globe box filled with dry air to avoid hydrolysis of WCl 6 by atmospheric humidity. The substrate coated with a nanocrystalline WO 3 thin film (5.25 cm 2 ) was soaked in the ethanol solution of WCl 6 and heated in a 100-mL Teflon-lined autoclave at 373 K for 20 h. No appreciable deposition was observed on the conductive glass in the absence of the base WO 3 nanocrystalline layer. After cooling to room temperature, the substrate was washed with water and dried at 393 K. The actual monomer for the nucleation and growth might be tungsten(VI) ethoxide produced by alcoholysis of WCl 6 upon dissolution in ethanol.…”

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Fabrication and photoelectrochemical property of tungsten(vi) oxide films with a flake-wall structure

2010

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Efficient visible light-induced photoelectrochemical oxidation of water was achieved using a tungsten(IV) oxide (WO 3 ) film composed of perpendicularly oriented plate-like crystallites, a flake-wall film, prepared on a transparent conductive substrate by controlling anisotropic crystal growth of tungsten oxide hydrate (WO 3 •H 2 O) followed by calcination.Water splitting using solar light is a key technology for the establishment of a low-carbon society. 1 Because of the positive Gibbs energy change in the water splitting, a direct one-step reaction may not proceed even though compensating energy is injected from outside the system, but it can be achieved by dividing into two parts: reduction of water to hydrogen and oxidation of water. Fujishima and Honda reported, for the first time, that photoirradiated titania and platinum electrodes could be used for the oxidation and reduction parts, respectively. 2 Although such a "photoelectrochemical" cell requires additional external energy as electrical or chemical bias to compensate the potential drop due to resistance of a circuit as well as overpotentials for the redox (electron transfer) reactions, the anode and cathode can be designed and their performance can be optimized separately and individually, which is the most significant merit of photoelectrochemical systems compared with particulate photocatalytic systems. Photoelectrochemical oxidation of water to evolve molecular oxygen is induced on an n-type semiconductor electrode by valence band holes generated by band-gap excitation. 3,4 Significant incident photon-to-current conversion efficiencies (IPCEs) for oxidation of water have been reported on WO 3 films, which are responsive to the blue part of visible light owing to the band gap of ca. 2.6 eV. 5-9 Nanocrystalline WO 3 films prepared by sol-gel techniques possessed porous network structures consisting of well-crystallized nanoparticles exhibiting a large surface area for semiconductor/liquid junctions. Since porous electrodes require a thickness of several micrometers to maximize light absorption, 10,11 the increase in thickness would increase grain boundaries, at which free electrons are scattered and recombination of photogenerated electron-hole pairs occurs, resulting in retardation of electron transfer to a back-contacted conductive substrate. 8,11,12 It has been reported that films composed of perpendicularly oriented crystallites showed higher photoelectrochemical performance than that of films with nanocrystalline particles. 11,13-16 For WO 3 , there have been few works focusing on the photoelectrochemical behavior of perpendicularly oriented crystalline films. 16 Herein, for the first time, WO 3 films consisting of perpendicularly oriented crystalline flakes were successfully fabricated by a wet process using anisotropic crystal growth of WO 3 •H 2 O with a layered crystal structure. Since the crystalline flakes were oriented normal to the substrate like a wall, we named this film a flake-wall film. Figure 1a shows the crystal structure of WO 3...

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Photoelectrochemical Properties of Nanostructured Tungsten Trioxide Films

Cited by 477 publications

References 26 publications

Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

A quantitative assessment of the competition between water and anion oxidation at WO3 photoanodes in acidic aqueous electrolytes

Fabrication and photoelectrochemical property of tungsten(vi) oxide films with a flake-wall structure

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Photoelectrochemical Properties of Nanostructured Tungsten Trioxide Films

Cited by 477 publications

References 26 publications

Synthesis and Characterization of Ultrathin WO3 Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

Synthesis and Characterization of Ultrathin WO3 Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

A quantitative assessment of the competition between water and anion oxidation at WO3 photoanodes in acidic aqueous electrolytes

Fabrication and photoelectrochemical property of tungsten(vi) oxide films with a flake-wall structure

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Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)

Synthesis and Characterization of Ultrathin WO₃ Nanodisks Utilizing Long-Chain Poly(ethylene glycol)