Understanding the effect of morphology on the photocatalytic activity of TiO₂ nanotube array electrodes

详细信息    查看全文

• 作者：C. Adá ; n ; J. Marugá ; n ; ^{javier.marugan@urjc.es" class="auth_mail" title="E-mail the corresponding author} ; E. Sá ; nchez ; C. Pablos ; R. van Grieken
• 关键词：TiO2 nanotubes ; Morphology ; Photocurrent ; Photocatalysis ; Photoelectrocatalysis
• 刊名：Electrochimica Acta
• 出版年：2016
• 出版时间：10 February 2016
• 年：2016
• 卷：191
• 期：Complete
• 页码：521-529
• 全文大小：1686 K

文摘

A comprehensive report on the correlation between the morphology and the photocatalytic (PC) and photoelectrocatalytic (PEC) activity of TiO₂ nanotubes (NTs) electrodes is presented. New insights are provided to support the effect of the anodization conditions on the photon-to-current efficiency of the electrodes based on the dimensional characteristics of the TiO₂-NTs. Electrodes with promising properties based on the characterization data were scaled-up to test their activity on the PC and PEC oxidation of methanol. Results indicate that the length of the nanotubes significantly influences the photodegradation efficiency. The enhancement achieved in both PC and PEC processes with longer nanotubes can be explained by the higher surface area in contact with the electrolyte and the increase in the light absorption as the TiO₂ layer becomes thicker. However, as the length of the nanotubes increases, a reduction in the enhancement achieved by the application of a potential bias is observed. Kinetic constants of both reactions (PC and PEC) tend to get closer and the charge separation effect diminishes. In relative terms, the effect of the electric potential is more pronounced for electrodes with the shorter NTs. The reason is that once the TiO₂ layer is thick enough to absorb the available radiation, a further increase in the NTs length increases the resistance of the electrons to reach the back contact and the diffusional restrictions to the mass transport of the reactants/products along the tubes. Consequently, the existence of a compromise between reactivity and transport properties lead to the existence of an optimal NTs length.