Mechanistic Aspects of the Self-Organization Process for Oxide Nanotube Formation on Valve Metals

Yasuda, Kouji; Macák, Jan M.; Berger, Steffen; Ghicov, Andrei; Schmuki, Patrik

doi:10.1149/1.2749091

Cited by 243 publications

(223 citation statements)

References 40 publications

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“…The electrochemical setup consisted of a 2 electrode configuration using a platinum foil as the counter electrode, while the titanium foils (working electrodes) were pressed against an had been used to anodize titanium at 60V, after the initial aging. As can be seen, in all cases the current transients show the typical behaviour reported in earlier papers [44,45]. Even though this behaviour was deeply described and verified in previous literature (for review see ref.…”

Section: Methodssupporting

confidence: 87%

Effect of electrolyte age and potential changes on the morphology of TiO2 nanotubes

Sopha

Hromádko

Nechvílová

et al. 2015

Journal of Electroanalytical Chemistry

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In the present work we report on the influence of the age of ethylene glycol-based electrolytes on the synthesis of self-organized TiO 2 nanotube layers. Electrolytes of different ages, defined by the total duration for anodization, were explored in order to get insight about how the tube structure changes with the electrolyte age. The results show a strong dependence of the electrolyte age upon the nanotube length and diameter -a phenomena surprisingly not discussed in existing literature. When fresh electrolytes are employed, nanotube arrays with a high aspect ratio are received, while in older electrolytes (i.e. already used for anodization) the nanotube arrays exhibit low aspect ratios. This is very important aspect for the reproducible synthesis of the nanotube layers. Moreover, the effect of the potential on the nanotube dimensions was investigated. Linear dependence of the diameter upon the potential was observed. Last, but not least, the influence of a potential change towards the end of the anodization time was studied. By sweeping the potential to 100 V, or to 5 V and keeping this for one hour after applying a constant potential of 60 V for 4 hours, nanotubes underwent interesting morphological changes. In particular, when slow sweeping from 60 V to 5 V was carried out, small nanotubes grew in the gaps between the initial nanotubes. Interestingly, these nanotubes layers showed lower adhesion to the underlying substrates.

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Section: Methodssupporting

confidence: 87%

Effect of electrolyte age and potential changes on the morphology of TiO2 nanotubes

Sopha

Hromádko

Nechvílová

et al. 2015

Journal of Electroanalytical Chemistry

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“…The obtained results suggest that the mechanism of selforganization of ZrO 2 nanotubes on zirconium seems to be similar to that suggested for titanium [35,36], though, probably, a more sophisticated approach is needed to model this electrochemical process [37]. Muratore et al [38,39] and Fang et al [34] pointed out the possible influence of compact and thin fluoride-rich layer formed during anodization on the tubular structure formation.…”

Section: Introductionsupporting

confidence: 66%

Synthesis of ZrO2 nanotubes in inorganic and organic electrolytes by anodic oxidation of zirconium

Stępień

Handzlik

Fitzner

2014

J Solid State Electrochem

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Present work reports on the results of the electrochemical growth of self-ordered zirconia nanotubes formed in aqueous Na 2 SO 4 +HF and nonaqueous electrolytes with glycerol addition. Anodization process was carried out in this inorganic water-based mixture with constant pH=2.5 and in the voltage range from 5 to 60 V. Similar experiments were repeated in an organic glycerol-based electrolyte with the voltage equal to 20 V and with variable glycerol concentration. All experiments were conducted at constant room temperature. The tube diameter dependence on the voltage of anodization process in an inorganic electrolyte was derived. It was found that when glycerol addition to water electrolyte was used, it takes more time to produce long zirconia nanotubes. However, they do not collapse as the similar structure of the same length formed in aqueous electrolyte.

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“…how much of the current goes into side reactions -namely oxygen evolution. If oxygen evolution becomes too high, the tube morphology turns into a sponge morphology [40,67] (Fig. 2e).…”

Section: Ii)mentioning

confidence: 99%

Anodic TiO2 nanotube layers: Why does self-organized growth occur—A mini review

Zhou

Nguyen

Özkan

et al. 2014

Electrochemistry Communications

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168

138

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The present review gives an overview of the highlights of more than 10 years of research on synthesis and applications of ordered oxide structures (nanotube layers, hexagonal pore arrangements) that are formed by self-organizing anodization of metals. In particular we address the questions after the critical factors that lead to the spectacular self-ordering during the growth of anodic oxides that finally yield morphologies such as highly ordered TiO 2 nanotube arrays and similar structures. Why are tubes and pores formed -what are the key parameters controlling these processes?Link to the published article: http://dx.doi.org/10.1016/j.elecom.2014.06.021 1 Over the past decade, the formation and application of anodic, self-organized TiO 2 nanotube arrays grown from a Ti metal (as illustrated in Fig.1) and similar oxide structures have attracted wide scientific and technological interest [1][2][3][4][5][6][7]. Self-organization during anodization has been observed already more than 70 years ago for aluminum that, when anodized in acidic electrolytes, forms hexagonally ordered porous structures [8] -such ordering can peak in a virtually perfect arrangement, as demonstrated by Masuda et al. in 1995 [9], by a meticulous optimization of the electrochemical growth conditions. These alumina structures since then have been widely used for templating (i.e., to fill the pores by a secondary material to form nanorods or nanowires, in combination with stripping the template or not), as well as for numerous other applications -excellent overviews on growth and applications of porous alumina are available; see e.g. refs. [2][3][4]10,11].In the past few years, however, research activities on ordered TiO 2 nanotube layers have in numbers of paper-output surpassed porous alumina; in the past decade, more than three thousand papers have been published dedicated to anodic TiO 2 nanotubes [1,[5][6][7]. The main reason for this enormous interest is the anticipated impact of such nanotube layers in functional applications of titanium dioxide; such as dye sensitized solar cells [12][13][14][15], photocatalysis [16,17] (including water splitting for the generation of hydrogen, pollution degradation, or the reduction of CO 2 ), biomedicine [18][19][20] (biomedical coatings of implants, drug delivery systems), ion-insertion batteries, electrochromics, etc. [21][22][23][24] These applications are, to a large extent, based on a number of almost unique features of TiO 2 [1,[25][26][27][28]: it is a semiconductor of a band-gap of 3.0 eV (rutile) -3.2 eV (anatase), with a considerably large electron diffusion length (mainly anatase), relative band-edge positions suitable to trigger a wide range of photocatalytic reactions; the material is highly biocompatible, and shows considerably good ion intercalation properties. Many of these features can be exploited in a nanotubular form even more beneficially than in powder assemblies (e.g. directional charge transport, orthogonal carrier separation, optimized and directional diffusion profile...

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Mechanistic Aspects of the Self-Organization Process for Oxide Nanotube Formation on Valve Metals

Cited by 243 publications

References 40 publications

Effect of electrolyte age and potential changes on the morphology of TiO2 nanotubes

Effect of electrolyte age and potential changes on the morphology of TiO2 nanotubes

Synthesis of ZrO2 nanotubes in inorganic and organic electrolytes by anodic oxidation of zirconium

Anodic TiO2 nanotube layers: Why does self-organized growth occur—A mini review

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