Electrochemical Method for Synthesis of a ZnFe2O4/TiO2 Composite Nanotube Array Modified Electrode with Enhanced Photoelectrochemical Activity
✍ Scribed by Yang Hou; Xin-Yong Li; Qi-Dong Zhao; Xie Quan; Guo-Hua Chen
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 801 KB
- Volume
- 20
- Category
- Article
- ISSN
- 1616-301X
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✦ Synopsis
Nanoscale-architectured titania, as a high-efficiency, low-cost photocatalyst, has attracted considerable interest because of its unique chemical and physical properties, and has been widely investigated for photocatalysis, water splitting for generation of hydrogen, dye-sensitized solar cells, electrochromic windows, and Li ion batteries. Very recently highly ordered TiO 2 nanotube arrays were synthesized by anodic oxidation of titanium and have generated considerable scientific interest. This simple and more controllable technique was received favorably and further developed by the academic community. In contrast to random nanoparticle systems where slow electron diffusion typically limits device performance, the precisely oriented nature of the crystalline (after annealing) nanotube arrays makes them excellent electron percolation pathways for vectorial charge transfer between interfaces. Furthermore, the nanotube-array architecture with high surface area ratio and free surface creates an unprecedented opportunity to harvest sunlight for energy conversion or photodegradation more efficiently than the randomly oriented nanoparticles or nanotubes prepared by the sol-gel process. Because the highly ordered TiO 2 nanotube arrays grows directly on the titanium substrate by anodic oxidation method, it also has a very strong mechanical strength. However, TiO 2 is a large bandgap semiconductor (bandgap of 3.2 eV (anatase)). The intrinsic material absorbs solar light in the UV region only, about 4%-5% of the solar spectrum. From the viewpoint of solar energy utilization, the development of the photocatalysts that can utilize visible light (l > 400 nm) efficiently is indispensable. Considerable work by many investigators has focused on improving the absorption of visible light of TiO 2 nanocrystalline by metal and non-metal doping. Although this doping of substitutional atoms improves the visible light absorption in TiO 2 photoelectrode, few of them give prospective satisfactory results because of the increase of carrier-recombination centers, thermal instability, or the requirement of expensive ion-implantation equipments. One of the promising strategies to this problem is the development of novel visible-light-active photocatalysts. Another promising solution is the combining TiO 2 with narrow bandgap semiconductors of suitable bandgaps (such as CdS, PbS, Bi 2 S 3 , CdSe, and CdTe ) to extend the absorption