TiO<sub>2</sub>−WO<sub>3</sub> Composite Nanotubes by Alloy Anodization: Growth and Enhanced Electrochromic Properties

Nah, Yoon‐Chae; Ghicov, Andrei; Kim, Doohun; Berger, Steffen; Schmuki, Patrik

doi:10.1021/ja807106y

Cited by 226 publications

(159 citation statements)

References 28 publications

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“…Other, supporting studies on the electrochromism in W-Ti oxide have been reported for films prepared by sputtering [16][17][18][19], chemical technology involving spraying [20][21][22] dipping [16,23] or spinning [24][25][26], electrodeposition [27,28] and anodization [29]. The enhanced stability has been investigated in depth in recent work on W-Ti oxide films made by sputtering [30,31] and chemical techniques [26].…”

Section: Introductionmentioning

confidence: 90%

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Arvizu

Triana

Stefanov

et al. 2014

Solar Energy Materials and Solar Cells

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Electrochromism in sputter-deposited W-Ti oxide films: Durability enhancement due to Ti. Solar Energy Materials and Solar AbstractThin films of W-Ti oxide were prepared by reactive DC magnetron sputtering and were characterized by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electrochromic properties were studied by cyclic voltammetry in an electrolyte of lithium perchlorate in propylene carbonate and by optical transmittance measurements. The addition of Ti significantly promoted the amorphous nature of the films and stabilized their electrochemical cycling performance and dynamic range for electrochromism.

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Section: Introductionmentioning

confidence: 90%

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Arvizu

Triana

Stefanov

et al. 2014

Solar Energy Materials and Solar Cells

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“…1 More recently, by anodization of titanium in fluoride-containing electrolytes, it is possible to form a similar morphology, that is, self-aligned nanotube arrays. [4][5][6][7] Apart from Al and Ti, self-organized growth of nanoporous or nanotubular oxide structures have also been reported for other valve metals, such as Nb, 8,9 Zr, [10][11][12] Ta, [13][14][15] and W, 16 and alloys, such as TiAl, 17 TiNb, 18 TiZr, 19 TiW, 20 TiMo, 21 and TiTa. 22 Some elements, upon anodization in aqueous fluoride electrolyte, tend to form nanotubular structures such as Ti, Zr, and Hf, whereas others, e.g., Ta, Nb, and W, tend to form nanoporous structures.…”

mentioning

confidence: 92%

Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy

Wei

Berger

Shrestha

et al. 2010

J. Electrochem. Soc.

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In this work, we report on the formation of highly aligned nanoporous or nanotubular oxide structures by anodization of Ti-Ta alloys in NH 4 F containing ethylene glycol electrolytes. We show that depending on the anodization conditions, either a hexagonally self-organized nanoporous layer or a nanotube array can be formed. Critical factors that decide on tube or pore formation are the water content of the electrolyte and the applied voltage. The present approach provides hexagonally packed oxide structures with an order comparable to that of the gold standard, anodized alumina. Layers of thicknesses Ͼ10 m and individual pore diameter in the range of 27-50 nm can easily be produced. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3490424͔ All rights reserved.Manuscript submitted August 13, 2010; revised manuscript received August 25, 2010. Published September 30, 2010 In the past few years, the electrochemical formation of selforganized nanoporous or nanotubular structures has attracted considerable attention from both the scientific and the technological community. Honeycomb-packed anodic Al 2 O 3 nanoporous films [1][2][3] represent one of the earliest and best-known examples for an almost ideal self-organizing electrochemical process. 1 More recently, by anodization of titanium in fluoride-containing electrolytes, it is possible to form a similar morphology, that is, self-aligned nanotube arrays. Some elements, upon anodization in aqueous fluoride electrolyte, tend to form nanotubular structures such as Ti, Zr, and Hf, whereas others, e.g., Ta, Nb, and W, tend to form nanoporous structures. Only very recently, first investigations were reported on the transition of the morphology from self-organized nanopore to nanotube structures depending on the specific anodization conditions. 12,17,23 In the present work, we investigate self-organizing anodization with an alloy that contains a typical tube formation element Ti and a typical pore formation element Ta. While in aqueous electrolytes, such an alloy forms only tubular structures, 22 we demonstrate in the present work that an organic electrolyte can induce transition to a porous structure with a virtually unprecedented degree of short-and longrange orders.Except for scientific interest in the feasibility of ordered oxide formation on these materials, Ti-Ta oxides are also of high technological significance. The oxide layers provide a very high corrosion resistance to surfaces, as Ta 2 O 5 is significantly more resistant than TiO 2 in almost any environment but particularly under cathodic reductive conditions. 24,25 Moreover, the alloy provides excellent biocompatibility but with a considerably lower average weight than pure Ta. Therefore, various Ti-Ta alloys are explored as candidates for biomedical implant materials. 26,27 In this context, the decoration of Ti implants with TiO 2 nanotubes has already shown a beneficial nature in view of cell response, 28,29 hydroxyapatite formation, 30 and for applications in drug delivery systems. 31,32 It is hence expe...

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“…115 Summarizing, experiments show that metal ion doping extends the absorption spectrum, but in most cases the localized nature of the photogenerated charges limits photocatalytic activity. A particularly advantageous method to dope TiO 2 NTs is to anodize alloys of Ti-X (X = W, Mo, Nb), [116][117][118] nanotubes which exhibited similar high conductivity and found that TiO 2 doped with 0.1 at% Nb at an optimal length of 7 μm could produce up to 1.0 mA/cm 2 of photocurrent. 125 In both sets of studies above, the introduction of large amounts of Nb or Ta had detrimental effects, leading the authors to suggest that these elements act as recombination centers at concentrations greater than the optimal concentration of 0.1 at% for both Ta and Nb.…”

Section: Tio 2 Photoanodes In Photoelectrochemical Applications: Modimentioning

confidence: 99%

Titania Nanotubes by Electrochemical Anodization for Solar Energy Conversion

Tsui

Zangari

2014

J. Electrochem. Soc.

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TiO 2 nanotube arrays (NTs) are a promising platform for the conversion of sunlight to electricity in photovoltaic systems or to fuels in photoelectrochemical solar cells. We overview the properties and functionality of the various components of TiO 2 NT-based devices, discuss their integration in the energy conversion system and summarize recent advances in the field. In particular, we discuss the electronic and charge transport properties of TiO 2 NTs that govern the device performance and efficiency. Since the main challenge for the practical use of TiO 2 is the inability to absorb visible light, particular attention is paid to available techniques for TiO 2 sensitization, extending absorption beyond the UV portion of the solar spectrum. These techniques include doping to alter the bandgap and pairing TiO 2 with dyes, inorganic narrow band-gap semiconductors, or metal nanoparticles that exhibit plasmonic behavior. Various catalysts have been successfully paired with TiO 2 to accelerate the photocatalytic reactions of interest; materials, synthesis methods and catalytic mechanisms will also be discussed. Finally, we give a prospective outlook on the future of TiO 2 nanotubes for photoelectrochemical applications and identify areas for future research.

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TiO₂−WO₃ Composite Nanotubes by Alloy Anodization: Growth and Enhanced Electrochromic Properties

Cited by 226 publications

References 28 publications

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy

Titania Nanotubes by Electrochemical Anodization for Solar Energy Conversion

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TiO2−WO3 Composite Nanotubes by Alloy Anodization: Growth and Enhanced Electrochromic Properties

Cited by 226 publications

References 28 publications

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Electrochromism in sputter-deposited W–Ti oxide films: Durability enhancement due to Ti

Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy

Titania Nanotubes by Electrochemical Anodization for Solar Energy Conversion

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TiO₂−WO₃ Composite Nanotubes by Alloy Anodization: Growth and Enhanced Electrochromic Properties