Study On The Photocatalytic Degradation Of Little Molecular Organic Pollution Formaldehyde

Photocatalysis is an attractive approach for environmental protection, energy transformation and functional group transformation because of its advantage such as low-temperature, non-energy intensity and non-pollution. Further improvement on photocatalysts' activity and efficiency and improvement on the utilization ratio of sunlight are the essential step to apply this novel technology. Choosing little molecular pollution-formaldehyde as the degradation objective is not only significant on the environmental protection, but also provides useful reference for the organic pollutions' completely decomposition. In this dissertation, both the TiO2 and perovskite ABO3 two systems are used in the photocatalytic degradation of formaldehyde and characterized by XRD,TG－DSC,TEM,XPS and so on. And we change the photocatalytic degradation from using UV light to using visible light, only to find the relationship between the photocatalytic activities and the photocatalysts.First of all, we study the photocatalytic degradation of formaldehyde under UV light with TiO2 system photocatalysts. We used sol-gel method to prepare well-distributed nano TiO2, and found the best preparation condition of it. Also, we used SiO2 modify the TiO2 photocatalyst, and found that adding a certain amount of SiO2 can improve the activity of TiO2. Secondly, under imitating sunlight we found nano perovskite LaCoO3 prepared by citric acid complex method has a certain activity of formaldehyde degradation. And we further discussed the influence of the B site ion to LaBO3. With different B site ion, the LaBO3 showed very different activities for the reaction, the regularity is: LaNiO3>LaCoO3>LaFeO3>LaMnO3>LaCrO3, this regularity has great relation with B ion radius, electron configuration and eletronegativity. Because the difference of B site ion leads to the difference of binding energy, the difference of gap energy and the difference of stimulated degree, and thus lead to the difference of photocatalytic activities. Finally, we discussed the photocatalytic activities of SrFeO3 and LaFeO3, and found that there exist two kinds of oxygen, crystal oxygen and adsorbed oxygen, on the surface of both SrFeO3 and LaFeO3. According to the results of XPS analysis, content of adsorbed oxygen in SrFeO3 is higher than in LaFeO3, and this lead to photocatalytic oxidation activity of SrFeO3 is higher than LaFeO3.