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Journal Articles Journal of Solid State Electrochemistry Year : 2013

Relation between morphology and conductivity in TiO2 nanotube arrays: an electrochemical impedance spectrometric investigation

Abstract

Two types of TiO2 nanotubular arrays were obtained by anodisation of a titanium foil, in two different solutions containing fluoride ions. For the first type which has rough tube walls, impedance measurements in the dark showed the presence of a localised surface state which was related to adsorbed molecular water. Under UV illumination, this adsorbed molecular water was photo-dissociated. Moreover, an increase of 2 orders of magnitude for the limiting capacitance of the space charge layer was observed, simultaneously with the disappearance of the localised state and with a 100-time increase of the carrier density associated with hydrogen insertion. The second type of layer was characterised by smoother tube walls, a high doping level (1020 cm−3) in the dark, a lack of localised states and no long-lasting photo-induced effect. In this case, the width of the space charge layer became rapidly higher than the half-thickness of the tube walls, when the applied potential increased. Therefore, the walls were progressively depleted under anodic polarisation, passing from a situation where the tubes were totally active in the cathodic range towards a situation where the contribution of the tube walls could be neglected.
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Dates and versions

hal-00785963 , version 1 (07-02-2013)

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Peng Pu, Hubert Cachet, Edgard Ngaboyamahina, Eliane Sutter. Relation between morphology and conductivity in TiO2 nanotube arrays: an electrochemical impedance spectrometric investigation. Journal of Solid State Electrochemistry, 2013, 17, pp.817-828. ⟨10.1007/s10008-012-1931-0⟩. ⟨hal-00785963⟩
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