Anodic growth of nanoporous WO3 films: Morphology, photoelectrochemical response and photocatalytic activity for methylene blue and hexavalent chrome conversion

Watcharenwong, Apichon; Chanmanee, Wilaiwan; Chenthamarakshan, C. R.; Kajitvichyanukul, Puangrat; Rajeshwar, Krishnan

doi:10.1016/j.jelechem.2007.09.030

Cited by 128 publications

(80 citation statements)

References 63 publications

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“…46 For the experiments we used an anodizing conventional electrochemical cell of two-electrode, the tungsten foil (2×2 cm) as working electrode and a Pt gauze as counterelectrode. A tungsten foil was immersed in NaF solution 0.15 mol L -1 as the supporting electrolyte, applying a ramp potential of 0.2 V s -1 until it reached 60 V, which was maintained for 2 h, 28 using a power supply 60 V/2 A stabilized Tectrol ® . After anodizing, the electrode was carefully washed by immersion in deionized water and dried under N 2 flow.…”

Section: Preparation Of W/wo 3 Thin Film Electrodementioning

confidence: 99%

“…: vacuum evaporation, 19 chemical vapor, 20,21 sol-gel precipitation, [22][23][24][25] spin coating, 26 sputtering, 27 and electrodeposition. [28][29][30][31][32][33][34] Although a sol-gel technique is one of the simplest and lowest-cost procedures selected for a wide range of applications, there have been only a few reports on photoelectrochemical characteristics of the WO 3 film prepared by a sol-gel technique. [5][6][7][8] Several techniques for improving photoresponse of thin film electrodes W/WO 3 have already been proposed.…”

Section: Introductionmentioning

confidence: 99%

“…However, studies focused on photocatalytical and photoelectrocatalytical processes using activation in the visible region are scarce, limiting to purification of water 39 and oxidation of some organics. 28,40,41,43 The basic red 51 dye, Figure 1, is a soluble dye widely used in several commercial formulations destined to semipermanent hair dyeing. 44 They are used as temporarily molecules deposited in the external structure of the hair by ionic forces involving interaction with protein fibers of the hair.…”

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confidence: 99%

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Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Zanoni¹

2011

J. Braz. Chem. Soc.

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Eletrodo nanoporoso auto-organizado de W/WO 3 pode ser obtido através da anodização eletroquímica de placas de W em solução de NaF 0,15 mol L -1 como eletrólito suporte, aplicando uma rampa de potencial de 0,2 V s -1 , até alcançar 60 V, mantendo por 2 h. A forma monoclínica altamente ordenada do WO 3 é majoritária quando calcinado a 450 0 C durante 30 min, obtendo uma maior fotoatividade quando irradiada na luz visível em relação a luz UV. O eletrodo promove a descoloração total do vermelho básico 51, utilizado em tinturas de cabelo, após 60 min de oxidação fotoeletrocatalítica, em densidade de corrente de 1,25 mA cm -2 e irradiação em comprimento de onda 420-630 nm. Nessa condição foi obtido 63% de mineralização. Uma menor eficiência é obtida para o sistema irradiado por comprimento de onda (280-400 nm), quando apenas 40% de remoção de carbono orgânico total é obtida, necessitando de 120 min de tratamento para a descoloração total da solução do vermelho básico 51.Self-organized W/WO 3 nanoporous electrodes can be obtained by simple electrochemical anodization of W foil in 0.15 mol L -1 NaF solution as the supporting electrolyte, applying a ramp potential of 0.2 V s -1 until it reached 60 V, which was maintained for 2 h. The monoclinic form is majority in the highly ordered WO 3 annealed at 450 °C , obtaining a higher photoactivity when irradiated by visible light than by UV light. The electrode promotes complete discoloration of the investigated basic red 51 dye after 60 min of photoelectrocatalytic oxidation, on current density of 1.25 mA cm -2 and irradiation on wavelength of 420-630 nm. In this condition it was obtained 63% of mineralization. Lower efficiency is obtained for the system irradiated by wavelength (280-400 nm) when only 40% of total organic carbon removal is obtained and 120 min is required for complete discoloration.Keywords: W/WO 3 electrodes, electrochemical anodization, photoelectrocatalysis, basic red 51, hair dye IntroductionThe use of TiO 2 as photoanode in photoelectrocatalytic degradation of pollutants is well known in literature. [1][2][3][4][5][6][7][8][9][10] Nevertheless, this material presents band gap energy around 3.2 eV, which is photoexcited only in the ultraviolet region (l ≤ 380 nm).11-14 Tungsten trioxide has been an excellent alternative material, since it presents smaller band gap energy (2.4-2.8 eV) and can be photoexcited in the visible region close to the UV region. [15][16][17][18] 28-34 Although a sol-gel technique is one of the simplest and lowest-cost procedures selected for a wide range of applications, there have been only a few reports on photoelectrochemical characteristics of the WO 3 film prepared by a sol-gel technique. [5][6][7][8] Several techniques for improving photoresponse of thin film electrodes W/WO 3 have already been proposed. The electrodeposited Pt/WO 3 catalysts have improved the oxidation of methanol and formic acid. [35][36][37][38] The WO x films with Pt, Sn, and Ru dopands were used for electrooxidation of acetaldehyde. Some authors have de...

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Section: Preparation Of W/wo 3 Thin Film Electrodementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Zanoni¹

2011

J. Braz. Chem. Soc.

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“…[1][2][3][4] Thus, various methods used to fabricate WO 3 are reported, such as evaporation, [5][6][7] spray pyrolysis, 8 pulsed layer deposition 9,10 and electrodeposition. 11,12 However, the electrochemical anodization method adopted in this work provides a simple and economic way of synthesizing targeted morphologies such as nanoporous or nanotube structures.…”

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confidence: 99%

Electrochromic Enhancement of WO₃-TiO₂Composite Films Produced by Electrochemical Anodization

Gui

Blackwood

2014

J. Electrochem. Soc.

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An enhancement of the electrochromic properties of WO 3 thin films by the incorporation of TiO 2 is presented. The composite films are obtained by anodizing co-sputtered tungsten / titanium on conductive glass substrates in 1 M H 2 SO 4 solution containing 0.3 wt% NaF. As the titanium content is increased from 0 to 15 at.% a morphology evolution occurs, from nano-porous to nano-flakes and finally to nano-blocks interweaved with nano-pores. The nano-flakes, obtained at 10 at% Ti, proved to be the most conducive structure for the insertion and removal of Li + ions such that this composition exhibits transmittance regulation abilities of 58.5%, 72% and 77.7% at 550 nm, 632.8 nm and 800 nm respectively, which are more than a 25% improvement at all wavelengths over a pure WO 3 film formed in the same way. The WO 3 /TiO 2 film with addition of 10 at.% Ti also has faster coloration/bleaching times, especially in the critical near infrared region with values of 10 s / 64 s at 800 nm compared with 32 s / 90 s of a pure WO 3 thin film, as well as improved stability losing less than 5% of its capacity after 1000 switching cycles. and electrodeposition. 11,12 However, the electrochemical anodization method adopted in this work provides a simple and economic way of synthesizing targeted morphologies such as nanoporous or nanotube structures. Unfortunately there are still drawbacks when compared to vacuum deposited films, for instance the electrochemically prepared WO 3 has poorer reversibility and stability as well as a shorter optical modulation range. This has led to interest in mixed metal oxide composite systems to compensate for these eficiencies. [13][14][15][16][17][18][19] To date, there are many reports on the doping or mixing other oxides with WO 3 to improve its electrochromic properties, with oxides of barium, 20 cobalt, 21 nickel, 22 molybdenum 23 and most successfully titanium.24 Even a small quantity of the guest oxide has a profound effect on the host's optical properties. Hashimoto and Matsuoka first reported in 1991 that an amorphous WO 3 -TiO 2 film, produced by electron beam deposition method, exhibits a longer life-time than a pure tungsten oxide film. 24 Subsequently, in 1993, Gottsche et al. 25 compared the electrochromic properties of mixed WO 3 -TiO 2 thin films fabricated by sputtering and sol-gel techniques. These authors point out that the addition of TiO 2 with molar percentages ranging from 10% to 15% reduced the crystallinity of WO 3 host and led to significant structural changes. Later, Wang and Hu successfully composed a TiO 2 -doped WO 3 film by spin coating and found that the Ti-addition stabilized the peroxotungstic acid in the spin coating solutions. 26 In 2005, Patil et al. 27 prepared WO 3 -TiO 2 films via a spray pyrolysis method and discussed the improved electrochromic reversibility and coloration efficiency.However, in these earlier works the coloration efficiency has not improved significantly to the level where it can be used in a practical smart window. Indeed, in some cases cert...

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“…14, No. 3,2011 열증착법 (thermal evaporation), 12,13) 졸-젤 코팅 (sol-gel coating), 14,15) 양극산화 (anodization) [16][17][18][19][20][21] (Fig. 1(b, f)), 빛을 조사하며 제조한 산화물 (Fig.…”

Section: 서 론mentioning

confidence: 99%

The Effects of Pre-Annealing on Electrochemical Preparation for Nanoporous Tungsten Oxide Films

Kim¹,

Kim²,

Choi³

2011

Journal of the Korean Electrochemical Society

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: We describe that the surface and thickness of nanoporous WO 3 fabricated by both light-induced and light-absent anodization are affected by pre-annealing process from 200 o C to 600 o C. As a result, the nanoporous WO 3 with a thickness of 1.83 µm can be achieved by anodization for 6 hours after pre-annealing at 400 o C without illumination of light. Moreover, the thickness of nanoporous WO 3 fabricated by pre-annealing is thicker than that of WO 3 prepared by non-annealing process. However, the light illumination during anodization leads to convert the crystalline structure obtained by pre-annealing, which interfere the growth of nanoporous WO 3 . In this paper, we discuss about the growth mechanism of these different nanoporous WO 3 films.

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Anodic growth of nanoporous WO3 films: Morphology, photoelectrochemical response and photocatalytic activity for methylene blue and hexavalent chrome conversion

Cited by 128 publications

References 63 publications

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Electrochromic Enhancement of WO₃-TiO₂Composite Films Produced by Electrochemical Anodization

The Effects of Pre-Annealing on Electrochemical Preparation for Nanoporous Tungsten Oxide Films

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Anodic growth of nanoporous WO3 films: Morphology, photoelectrochemical response and photocatalytic activity for methylene blue and hexavalent chrome conversion

Cited by 128 publications

References 63 publications

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

Electrochromic Enhancement of WO3-TiO2Composite Films Produced by Electrochemical Anodization

The Effects of Pre-Annealing on Electrochemical Preparation for Nanoporous Tungsten Oxide Films

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Electrochromic Enhancement of WO₃-TiO₂Composite Films Produced by Electrochemical Anodization