Oxide Semiconductors Nano-Crystalline, Tubular and Porous Systems

OXIDE SEMICONDUCTORS NANO-CRYSTALLINE, TUBULAR AND POROUS SYSTEMS 

The thermodynamic potential for splitting water into H2 and O2 at 25°C is 1.23 V. Considering overvoltage losses the actual voltage required for water dissociation is in the range of 1.6 to 1.8 V. A 650 nm wavelength, which is in the lower-energy red portion 

This chapter considers the fabrication of oxide semiconductor photoanode materials possessing tubular-form geometries and their application to water photoelectrolysis due to their demonstrated excellent photo-conversion efficiencies particular emphasis is given in this chapter to highly-ordered Ti02 nanotube arrays made by anodic oxidation of titanium in fluoride based electrolytes. Since photoconversion efficiencies are intricately tied to surface area and architectural features, the ability to fabricate nanotube arrays of different pore size, length, wall thickness, and composition are considered, with fabrication and crystallization variables discussed in relationship to a nanotube-array growth model. 

Metal oxide nanotubes have been synthesized by a diverse variety of fabrication routes. For example titania nanotubes, and nanotube arrays, have been produced by deposition into a nanoporous alumina template [48-51], sol-gel transcription using organo-gelators as templates [52,53], seeded growth [54], hydrothermal processes [55-57] and anodic oxidation [58-65]. 

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Oxide Semiconductors Nano-Crystalline, Tubular and Porous Systems... 

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