Σύνθεση νανοκρυσταλλικών ημιαγώγιμων οξειδίων χαρακτηρισμός και μελέτη των εφαρμογών τους στη φωτοκαταλυτική και φωτοηλεκτροχημική διάσπαση του ύδατος

Abstract

Nanocrystalline titanium dioxide films, with deposited noble metals on their surface were studied for the photocatalytic production of Η2, through the so-called “photocatalytic reforming” processes. These films were deposited on glass substrates by using sol-gel procedures, carried out in the presence of acetic acid and a surfactant template, Triton X-100. The titania films consist of anatase nanocrystals, of about 12 nm average particle size. They were highly hydrophilic and were strong adsorbers of positively charged organic substances. Photodegradation of adsorbed dyes was very efficient on these titania nanoparticulate films. Photocatalytic hydrogen production was studied by using nanocrystalline films of Pt/TiO2. Pt gave the best results concerning photocatalytic activity of titanium dioxide. The best conditions of platinum deposition, through its adsorption from aqueous solutions, were 30 min of adsorption in the dark from an aqueous solution of Na2PtCl4, having a concentration of 5*10-4 M, followed by the reduction of the adsorbed ions of Pt (II) by UV treatment. Using this type of photocatalyst lead to high efficiency of photodegradation of alcohols and generally products, derived from biomass in aqueous solutions. From all the compounds examined, ethanol and glycerol gave the highest photocatalytic hydrogen production rates. The photocatalytic reforming reaction, was carried out using UVA (black light, ~360 nm) radiation, that comes from low-energy black light sources and was applied on chemical compounds that have the general chemical structure of CxHyOz. Several categories of substances may have this structure, such as alcohols, saccharides, polyols and organic acids. Also, photocatalytic nanocrystalline films Pt/TiO2 led to substantially efficient process of hydrogen production, by using colloidal dispersions of oil-in-water microemulsion. The whole process of photocatalytic reforming of several substances can be a very attractive and very promising process, by employing nanocrystalline titania films, Pt/TiO2.