Electrochemical tuning of titania nanotube morphology in inhibitor electrolytes

Amrita Centre for Nanosciences, Amrita Institute of Medical Science & Research Centre, Amrita Vishwa Vidyapeetham, Elamakkara P O, Cochin 682 041, Kerala, India
Electrochimica Acta 01/2010; 55:3713. DOI: 10.1016/j.electacta.2009.12.096
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    ABSTRACT: Nanoporous anodic titanium oxide (ATO) layers with different cell sizes, pore diameters and the thicknesses are successfully grown by three-step self-organized anodization in ethylene glycol containing 0.38 wt% of NH4F and 1.79 wt% of H2O at applied potential differences ranging from 30 V to 70 V at various electrolyte temperatures. A relatively high growth speed (about 40 μm h−1) of nanopore arrays is achieved at 30 °C under the potential difference of 70 V. The morphology and the structure of ATO layers are directly affected by anodizing conditions, especially temperature and potential difference. It was found that the oxide thickness and the cell size are linearly dependent on anodizing potential difference. On the other hand, the anodizing temperature in the range of 10–30 °C does not affect the cell size in ATO films. Analyses of the pore diameter, pore circularity and regularity of the pore arrangement suggests that nanoporous anodic titania with the best pore arrangement can be formed in a controlled manner by anodization performed at 50 V and 20 °C. Surprisingly, below and above this critical potential difference and temperature, pore diameters are smaller and obtained ATO structures are less regular. At higher anodizing temperatures, the regularity of pore arrangement observed at the surface and the pore diameter are considerably affected by the precipitated hydrous titanium dioxide.
    Electrochimica Acta 11/2013; 104:526–535. · 4.09 Impact Factor
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    ABSTRACT: Anodic, self-organized TiO2 nanotubes were grown in different organic, fluoride ion containing electrolytes. The present work reports on a number of fundamental differences in tube morphology and composition, if nanotube layers are grown in either ethylene glycol, diethylene glycol, and dimethyl sulfoxide based electrolytes. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    physica status solidi (RRL) - Rapid Research Letters 06/2010; 4(8-9). · 2.39 Impact Factor
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    ABSTRACT: Although one-dimensional anodic TiO2 nanotube arrays have shown promise as supercapacitor electrode materials, their poor electronic conductivity embarrasses the practical applications. Here, we develop a simple electrochemical doping method to significantly improve the electronic conductivity and the electrochemical performances of TiO2 nanotube electrodes. These TiO2 nanotube electrodes treated by the electrochemical hydrogenation doping (TiO2-H) exhibit a very high average specific capacitance of 20.08 mF cm−2 at a current density of 0.05 mA cm−2, ∼20 times more than the pristine TiO2 nanotube electrodes. The improved electrochemical performances can be attributed to ultrahigh conductivity of TiO2-H due to the introduction of interstitial hydrogen ions and oxygen vacancies by the doping. The supercapacitor device assembled by the doped electrodes delivers a specific capacitance of 5.42 mF cm−2 and power density of 27.66 mW cm−2, on average, at the current density of 0.05 mA cm−2. The device also shows an outstanding rate capability with 60% specific capacitance retained when the current density increases from 0.05 to 4.00 mA cm−2. More interestingly, the electrochemical performances of the supercapacitor after cycling can be recovered by the same doping process. This strategy boosts the performances of the supercapacitor, especially cycling stability.
    Electrochimica Acta. 01/2014; 116:129–136.


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Sep 23, 2014