(36b) Titania Nanotubes as Templates for the Solar Production of Hydrogen

Titania nanotubes have recently emerged as a promising technology that may perhaps lead to the economically viable production of solar hydrogen through the photocatalytic splitting of water. The nanotube morphology does not only increase catalytic surface area but also appear to have superior light absorption and reduced charge recombination benefits. Different techniques for the electrochemical fabrication of nanotube arrays will be discussed and their light absorption properties will be evaluated through reflectivity and photocurrent measurements. The natural absorption spectrum of titania does not extend beyond the UV. It is clear that in order to fabricate a feasible device for the solar production of hydrogen this absorption spectrum has to be extended into the visible part of the solar spectrum. This can be done either by doping or by combining the titania with materials or dyes photoactive within the visible part of the spectrum. Electrochemical, thermal evaporator and CVD options for depositing materials photoactive in the visible range will be discussed.