Enhanced Photoelectrocatalytic Degradation of Methylene Blue on Smooth TiO[sub 2] Nanotube Array and Its Impedance Analysis

Abstract

The smooth titania nanotube array fabricated via two-step anodization in F− -containing ethylene glycol electrolytes plus a postcalcination has been developed as a photoelectrocatalytic (PEC) application on degradation of methylene blue (MB). It was found that the MB degradation kinetics meets the law of first-order reaction, and the rate constants of MB degradation were 0.147normalh−1 for photocatalytic (PC) process and 0.853normalh−1 for PEC process, a 5.8-fold increase under the condition of open-circuit and zero applied potential, respectively. Electrochemical impedance spectroscopy was used to analyze the enhanced degradation phenomenon in PEC as compared to PC on such electrodes, and the results revealed that the enhanced degradation efficiency of PEC process should be ascribed to the systematic change of capacitance and resistance and thus leading to a dramatic decrease of impedance on the interface of semiconductor under combination of illumination and bias potential. Further investigation revealed that the crystal structure of TinormalO2 nanotube array and the width of its space charge layer, which is mainly determined by the thickness of the nanotube wall as well as the potential applied across the wall of the nanotube, might be critical factors for the enhancing degradation efficiency due to its effective charge separation.

Photocatalytic reduction of methylene blue by TiO2 nanotube arrays: effects of TiO2 crystalline phase

“…Panel (b) shows the semilog plots of the decay of the absorption intensity at 665 nm with time. The linearity is consistent with the firstorder reaction of methylene blue reduction [40], and from linear regression the pseudo-first-order rate constant was estimated to be 2.42 9 10 -2 min -1 . The photocatalytic activity of the TiO 2 nanotubes annealed at other temperatures was evaluated in a similar fashion.…”

Self-organized TiO2 nanotubes in mixed organic–inorganic electrolytes and their photoelectrochemical performance

“…Titanium oxide (TiO 2 ) is one of the most widely studied semiconductor materials because of its promising potential applications, such as gas sensing devices [1,2], self-cleaning materials [3,4], solar cells [5,6], photocatalysts [7][8][9][10], and biomaterials [11,12]. Over the past several years, TiO 2 nanostructures have become the focus of considerable interest due to their unique properties.…”

ZnO and TiO2 1D nanostructures for photocatalytic applications

“…Photocatalysis has been intensively investigated in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In a photocatalytic process, electron-hole pairs are generated under illumination, followed by oxidation and/or reduction reactions at the surface of the photocatalyst [1].…”

“…In the presence of a photocatalyst, organic contaminants can be oxidized directly by a photogenerated hole or indirectly via reaction with reactive oxygen species (ROS), such as hydroxyl radical OH • , produced in the solution [1]. TiO 2 is a widely used photocatalyst material [1][2][3][4][5][6][7]. It exhibits photocatalytic activity under UV illumination [1].…”