Modification of TiO2 nanotube arrays by solution coating

Packed and sintered titania (TiO2) nanoparticles are conventionally used as a photoanode for dye-sensitized solar cells. As a result, barriers are created for the electron transport and electron-hole recombination due to the large number of interfacial boundaries and voids in such a mesoporous photoanode. A high aspect ratio of length/diameter of titania nanotube arrays (TNAs) is required to meet the high surface area and the reduction of interfacial boundaries. TNAs prepared by the organic anodic oxidation method in this work possess a vertical nanotube structure that exhibits a high surface area, high degree of crystallinity, geometric pre-orientation and active electro-optical nanograins. Such a synthesized mesoporous structure is typically obtained by 60 V/2 h and 450 °C/30 min post-annealing and has a tube diameter of 110 nm, and a tube length of 15 mm. When the TNAs are modified by a TiO2 nano-layer (TNL), the photocatalytic efficiency for methylene blue (MB) decomposition is further improved by up to 90%. Photosensitivity shows an obvious improvement when illuminating the UV light for the TNL modified TNAs and the visible light for the CuInS2 layer modified TNAs.