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Abstract: In this work, the homogeneous and heterogeneous degradations of diphenamid (DPA) in aqueous solution were conducted by direct photolysis with UVC (254nm) and by photocatalysis with TiO2/UVA (350nm), and the experimental results were compared. It was found that the homogeneous photolysis by UVC irradiation alone was quite efficient to degrade DPA up to 100% after 360min, but was very inefficient to mineralize its intermediates in terms of dissolved organic carbon reduction of only 8%. In contrast, the heterogeneous photocatalysis with TiO2/UVA showed relatively a lower degree of DPA degradation (51%), but a higher degree of its mineralization (11%) after 360min. These results reveal that the photocatalysis process has relatively poor selectivity to degrade different compounds including various intermediates from the DPA degradation, which is beneficial to its mineralization. In addition, over 20 intermediates were identified by LC–MS and 1H NMR analyses. Based on the identified intermediates, the reaction mechanisms and the detailed pathways of the DPA degradation by photolysis and photocatalysis were proposed, and are presented in this paper. [Copyright &y& Elsevier]

In this study titanium dioxide nanotube (TNT) arrays were prepared by an anodic oxidation process with post-calcination. The morphology and structure of the TNT films were studied by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the TNT films was evaluated in terms of the degradation of 2,3-dichlorophenol in aqueous solution under UV light irradiation. The effects of the nanotube structure including tube length and tube wall thickness, and crystallinity on the photocatalytic activity were investigated in detail. The results showed that the large specific surface area, high pore volume, thin tube wall, and optimal tube length would be important factors to achieve the good performance of TNT films. Moreover, the TNT films calcined at 500°C for 1h with the higher degree of crystallinity exhibited the higher photocatalytic activity than other TNT films calcined at 300 and 800°C. Consequently, these results indicate that the optimization of TiO2 nanotube structures is critical to achieve the high performance of photocatalytic reaction. [Copyright &y& Elsevier]

Abstract: In this study, polythiophene–TiO2 nanotube films (PTh/TNT) were successfully prepared by a two-step electrochemical process of anodization and electropolymerization, in which a highly ordered TiO2 nanotube (TNT) film was anodized at a low-voltage with post calcination first and then the prepared TNT film was deposited with a polythiophene layer by electropolymerization in the BFEE electrolyte. The morphology and structures of PTh/TNT composites were examined by FESEM, EDX, XRD and XPS methods. XPS spectra of PTh/TNT composites indicate the strong interaction between S sites of polymer backbone and TiO2 nanotubes, in which electron transfer from polythiophene to titania takes place. UV–vis DRS analysis shows that these composites have a strong photoresponse in the visible region at 500nm. The prepared PTh/TNT films revealed significant activity for 2,3-dichlorophenols (2,3-DCP) degradation under visible light irradiation and also sunlight irradiation, in which the PTh3/TNT film achieved the best performance. On the other hand, this study also confirmed that the side-chains of polythiophene could influence its photocatalytic activity significantly in an order from high to low as poly3-methylthiophene≈polythiophene>polythiophenecarboxylic acid>poly3-hexylthiophene. The results may provide useful information to further develop some effective polymer-semiconductor catalysts for pollutant degradation under sunlight irradiation for water and wastewater treatment. [Copyright &y& Elsevier]

In this study, the highly-ordered TiO2 nanotube (TNT) arrays on titanium sheets were prepared by an anodic oxidation method. Under UV illumination, the TNT films demonstrated the higher photocatalytic activity in terms of 2,3-dichlorophenol (2,3-DCP) degradation in aqueous solution than the conventional TiO2 thin films prepared by a sol–gel method. The effects of dissolved oxygen (DO) and pH on the photocatalytic degradation of 2,3-DCP were investigated. The results showed that the role of DO in the 2,3-DCP degradation with the TNT film was significant. It was found that 2,3-DCP in alkaline solution was degraded and dechlorinated faster than that in acidic solution whereas dissolved organic carbon removal presented an opposite order in dependence of pH. In the meantime, some main intermediate products from 2,3-DCP degradation were identified by a 1H NMR technique to explore a possible degradation pathway. A major intermediate, 2-chlororesorcinol, was identified from the 2,3-DCP decomposition as a new species compared to the findings in previous reports. Photocatalytic deactivation was also evaluated in the presence of individual anions (, Cl−, , and ). The inhibition degree of photocatalytic degradation of 2,3-DCP caused by these anions can be ranked from high to low as >Cl− > > . The observed inhibition effect can be attributed to the competitive adsorption and the formation of less reactive radicals during the photocatalytic reaction. [Copyright &y& Elsevier]

Abstract: It is well known that the structural disorder of photocatalyst nanopowder usually leads to the enhanced scattering of free electrons, and thus reduces the electron mobility; in contrast, an ordered and interconnected nanostructure favors to improve electron transport, then achieving the higher photocatalytic efficiency. Therefore, in this study, a highly ordered and coaxial WO3/TiO2 nanostructure, consisting of nanotubes and nanorods, was prepared by a sol–gel template technique. The obtained photocatalysts were characterized by FE-SEM, XRD, UV–vis DRS and PL measurement. These photocatalysts exhibited a strong photoresponse in the visible region and a low PL emission. Their photoactivity was evaluated by means of the degradation of 2,3-dichlorophenol (2,3-DCP) under visible light irradiation. Experimental results show that while there was no obvious degradation of 2,3-DCP with the TiO2 nanotubes as photocatalysts, ∼53% of degradation degree in 300min was obtained with the WO3/TiO2 nanocomposites. This significant activity should be attributed to the role of WO3 loaded in TiO2 nanotubes. The WO3 loading not only facilitates the effective separation of photogenerated carriers occurring on the TiO2 surface, but also enhances the surface hydroxyl groups and surface acidity, thus improving the overall photocatalytic performance. [Copyright &y& Elsevier]