Strong photoresponse of nanostructured tungsten trioxide films prepared via a sol–gel route

Yang, Bin; Barnes, Piers R. F.; Bertram, W.K.; Luca, Vittorio

doi:10.1039/b702097j

Cited by 71 publications

(45 citation statements)

References 29 publications

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“…S1 in ESI), which is close to the previously reported potentials for a WO 3 electrode. [5][6][7][8] This negative shift of the onset potential suggests that direct hole transfer to methanol to form CH 2 OH radical is more efficient than to water to form hydroxyl radical. 6 Since the CH 2 OH radical exhibited the large negative redox potential, which can transfer an electron to the conduction band of WO 3, the possibility of back-electron transfer is expected to be negligible.…”

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confidence: 99%

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

2010

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“…High incident photonto-current conversion efficiency has been reported for nanocrystalline films of tungsten oxide ͑WO 3 ͒ with a large interface of semiconductor/liquid. [4][5][6][7][8][9][10][11] The nanocrystalline films require thickness of several micrometers to maximize absorption of incident photons, while an increase in the thickness would increase the density of grain boundaries, resulting in the retardation of electron transport to the back-contacted conductive substrate due to resistance ͑Fig. 1a͒.…”

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Photoelectrochemical Property of Tungsten Oxide Films of Vertically Aligned Flakes for Visible-Light-Induced Water Oxidation

Amano¹,

Ding²,

Ohtani³

2011

J. Electrochem. Soc.

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A vertically arrayed flake film, "flake-wall film," of monoclinic tungsten oxide ͑WO 3 ͒ was prepared on a transparent conductive glass by controlling anisotropic crystal growth and self-arrayed growth of WO 3 hydrate with a layered crystal structure. The WO 3 flake-wall film exhibited superior performance for photoelectrochemical water oxidation under visible-light irradiation compared to that of a film consisting of horizontally laminated WO 3 flakes. The small differences between photocurrents under front-side irradiation and back-side irradiation and between photocurrents in the absence and the presence of methanol indicate the excellent electron transport property and long photogenerated carrier lifetime in the flake-wall film.

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“…The porosity increases furthermore the light absorption, because light scattering inside a nanoporous film is higher as compared with a dense film. Apart from solegel methods [10], electrochemical anodization [11] and reactive magnetron sputtering [12], the dealloying process is one of the most promising methods for preparing high surface area electrode materials. Dealloying has been used mostly to synthesize nanoporous metallic materials.…”

Section: Introductionmentioning

confidence: 99%

Combinatorial development of nanoporous WO3 thin film photoelectrodes for solar water splitting by dealloying of binary alloys

Stepanovich

Sliozberg

Schuhmann

et al. 2012

International Journal of Hydrogen Energy

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Strong photoresponse of nanostructured tungsten trioxide films prepared via a sol–gel route

Cited by 71 publications

References 29 publications

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

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

Photoelectrochemical Property of Tungsten Oxide Films of Vertically Aligned Flakes for Visible-Light-Induced Water Oxidation

Combinatorial development of nanoporous WO3 thin film photoelectrodes for solar water splitting by dealloying of binary alloys

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