ENHANCED PHOTOCATALYTIC ACTIVITY OF Ta2O5/SiO2 MIXED OXIDES

摘要

Semiconductor oxides like TiO2 and Ta2O5 are useful in water purification due to their ability to participate in heterogeneous photocatalytic reactions, which enable them to efficiently break down certain organic pollutants. When exposed to light with a photon energy greater than the semiconductor bandgap, the photocatalyst’s excited electron shifts from the valence band to the conductance band causing the formation of an electron-hole pair (e~- and h~+). When the electron and the hole migrate to the water/surface interface, they are free to participate in redox reactions that break down organics by oxidation. A requirement for initiation of the photoreaction in heterogeneous catalysis is the adsorption of the reactants to the semiconductor photocatalyst. Also, the photoreaction can proceed only if the photoelectrons and photoholes do not recombine inside the semiconductor surface or at the surface prior to involvement in redox reactions. Thus, the efficiency of the photoreactions can be improved by increasing adsorption of the pollutant to the catalyst (or, in general, increasing access to the pollutant) and/or lowering the recombination reaction rate between photo-generated holes and electrons.