NANOSTRUCTURED PHOTOCATALYTIC TITANIA THIN-FILMS: THE EFFECT OF FILM MORPHOLOGY ON PHOTOELECTROCHEMICAL PROPERTIES

摘要

Hydrogen has been touted as the fuel of the future. Since hydrogen is an element, it contains no carbon, and its use as a fuel, either in combustion or in a fuel-cell, leads to only water as a byproduct. Current techniques for hydrogen generation, however, rely upon steam reforming of hydrocarbons. This is problematic because the 1) hydrocarbons are produced on geologic timescales, which are much slower than current consumption requirements, and 2) the byproducts are carbonaceous greenhouse gasses. The photosplitting of water using solar energy is a potentially clean and renewable source of hydrogen fuel that is environmentally benign and easily distributed. Light impacting titanium dioxide electrodes immersed in water causes the water to split into oxygen and hydrogen. However, pure bulk TiO_2 requires UVlight (which is less than 5% of incident solar radiation) for excitation. Recent reports in the literature have indicated that some materials such as In_(1- x)Ni_xTaO_4 and WO_3 doped titanium dioxides are capable of harvesting visible sunlight to produce hydrogen and oxygen. The synthesis of such materials remains a challenge, since these compounds are produced by multi-step processes which are often difficult to replicate and even more difficult to scale-up. Advances in gas phase nanoparticle synthesis techniques offer hope that such materials could be synthesized that achieve breakthroughs in photocatalysis.