Photocatalysts chemical properties

Another interesting feature of the AMO photocatalysts is the effect of diluent substrates such as MgO or activated C. Addition of substrates causes an increase in the rate of photoassisted catalytic oxidation of isopropanol. A synergistic effect is clear specific amounts of diluent lead to an increase. Too much or too little diluent leads to a decrease in rate. The exact explanation of this synergistic effect is not known, however, it may related to the ability of species such as OH or adsorbed hydrocarbons and intermediates to travel back and forth across the AMO/substrate interface. There does not seem to be a correlation of rate with the surface area, acid base character, particle size or other physical/chemical properties of the substrate. 

These results demonstrate tliat shock-wave synthesis is a novel metliod to prepare nanosized materials with some unique physical and chemical properties. In the light of the experimental results, nanosized zinc ferrite and nickel ferrite synthesized by shock-wave treatment may Iiave potential applications as magnetic materials and photocatalysts. 

ZnO photocatalyst can also be coupled with other materials in order to improve its chemical and physical properties [183] and photocatalytic activity [184]. Nanosized ZnO was immobilized on aluminum foil for the degradation of phenol [185]. Lanthanum and ZnO were combined to degrade 2,4,6-trichlorophenol [186]. Compared with Ti02 nanomaterial, ZnO nanomaterial generally absorbs a significant amount of the solar spectrum in the visible range therefore, ZnO nanomaterials were combined with Ti02 nanomaterials used as a photocatalyst [187]. 

An increasing interest in studying silver particles and clusters adsorbed on titanium dioxide surface is provided by the efficiency of such systems as photocatalysts. Their catalytic properties are more evident than those of individual Ti02, both anatase and rutile-anatase mixture. There are few publications devoted to quantum chemical calculations of metal clusters adsorbed on TiOz surface at the modem level of theory. Besides, existing theoretical data describe adsorption of silver atom on mtile surface only. 

T24.5 Delafossite is a mineral with chemical composition CuFe02- Its structure has been described in Pabst, A. (1938) American Mineralogist, 23, 175-176, and more recently revisited (with a look at electronic properties of this material) in Marquardt, M., Ashmore, N Cann, D. (2006). Thin Solid Films, 496(1), 146-156. Connect this research with the fact that Fe 03 can also be used as a photocatalyst, as mentioned in Section 24.17 Photocaialysis. 

A good photocatalyst should be photoactive, able to use visible or near UV hght, biologically and chemically inert, photostable, and non-toxic. Over the years, many semiconductors with photocatalytic properties have been investigated of which TiO, and ZnO are prominent. TiO, a UV active photocatalyst, can use only 3.5% of the visible spectrum while artificial UV sources are expensive and difficult to handle [4]. The main advantage of using ZnO photocatalyst is its photoactivity in visible region and non-toxicity. 

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