Theoretical Study On Several Important Parameters Affecting Photocatalytic Activity

Since Fujishima and K.Honda discovered that TiO2 can split water into hydrogen and oxygen under the illumination in 1972,the photocatalytic discipline was born.Over the past decades,after a large number of people’s unremitting efforts,a great breakthrough has been made in the application and research of photocatalysis.However,these breakthroughs are mainly in the synthesis,characterization and catalytic activity of photocatalysts.There are few theoretical studies on Photocatalysis.In this paper,the effect factors of photocatalytic reaction temperature,catalyst particle size,photocatalyst and dielectric constant of doped photocatalyst valence degeneracy elimination on the photocatalytic activity have been researched theoretically.This paper mainly includes the following parts:1.Study on the effect of photocatalytic reaction temperature on photocatalytic activity.In this part,from these two aspects,the effect of temperature to electron hole-photoelectron number and redox activity of electron hole-photoelectron,we studied the relationship between the reaction temperature and photocatalytic activity theoretically.We studied the second aspect in the two conditions of that the interaction between the groups on the surface of the photocatalyst and the redox molecules is mutual attraction,mutual exclusion.We derived the relationship between the reaction temperature and the photocatalytic activity in the three cases of that the interaction between the groups on the surface of the photocatalyst and the redox molecules is mutual attraction,mutual exclusion,mutual attraction and exclusion.2.Study on the effect of particle size of photocatalyst on photocatalytic activity.In this part,from aspects of the total contact area between the photocatalyst particles and the molecules oxidized and deoxidized by the electron holes and photoelectrons,the residence time of the molecules oxidized and deoxidized by the electron holes and photoelectrons on the surface of the photocatalyst and oxidation ability and reduction ability of electron hole and photoelectron of photocatalyst,we analysed and derived the relationship between photocatalytic activity and photocatalyst particle size theoretically.The reason for the good photocatalytic activity of the photocatalyst with small particle size is explained theoretically.3.Study on the effect of the dielectric constant of photocatalyst on photocatalytic activity.This is the first time to study the relationship between the dielectric constant and the photocatalytic activity of the photocatalyst.In this part,the relationship equation between the photoelectron lifetime of the conduction band of photocatalyst and the dielectric constant of photocatalyst is derived.According to the photocatalytic mechanism and the derived equation,the relationship between the photocatalytic and the dielectric constant of the photocatalyst is elucidated as follows: the larger dielectric constant of the photocatalyst,the better the photocatalytic activity.4.Study on the effect of doped photocatalyst valence band degeneracy elimination on photocatalytic activity.This is the first time to study the relationship between the doped photocatalyst valence band degeneracy elimination and the photocatalytic activity.The effect of doped photocatalyst valence band degeneracy elimination reduced the valence band degeneracy of intrinsic semiconductor photocatalyst and reduced the number of electron in the valence band that can jump to the conduction band,and the energy level degeneracy elimination of impurity doped photocatalyst can cause these anomalies,namely,the band gaps of some doped photocatalysts are narrower than the intrinsic semiconductor photocatalyst,but the photocatalytic activity of the intrinsic semiconductor photocatalyst are better than these doped photocatalysts.