What is photocatalyst
The term photocatalysts consists of the combination of photochemisty and catalysis and implies that light and a catalyst are necessary to bring about or to accelerate a chemical transformation. Photocatalyst can be induced photoreaction by the presence of a catalyst with the light with various photocatalysts, the titanium dioxide is wide used because it has stable about acid-base condition and harmless about human body.
The mechanism of photocatalyst
When a photon with an energy of h υ matches or exceeds the energy band gap, Eg, of photocatalyst TiO2 ,
as a n- type semiconductor, an electron, ecb?, is prompt from the valence band into?the conduction band,
leaving the hole, hvb+, in valence band.
The hvb+ means the hole in the valence, ecb? ,means the excited electron in conduction band and we called the charge pair "hvb+ - ecb? ". The hole produce hydroxyl radicals(-OH) to oxidation of surface bound H2O, electrons are transferred to oxygen of obsorbed surface TiO2 so that produce super oxide (O2?).
The role of the hole and electrons at the surface of TiO2 in heterogeneous have a oxidants(or reductant).
These oxidants decompose organic materials into carbon dioxide (CO2) and water(H2O) etc.
This photocatalyst TiO2 used for clean up pollution in the air and water and sterization, corruption-control and deodorization etc.
