Modified Tio <sub> 2 </ Sub> Surface Photovoltaic Properties And Its Mechanism

In recent years, semiconductor function materials have attracted significant interest. Especially, nano-sized TiO₂ is paid the extensive attention because of its various merits, such as nontoxicity, long-term stability and high photocatalytic activity. Therefore, it has several promising applications in the photoelectric chemistry and photocatalysis. TiO₂ photocatalysis has two bottleneck factors, including low quantum efficiency and low efficiency for utilizing solar light. This paper has discussed and explored the method of improving the separation rate of photo-induced carriers by surfactant for bottlenecks of nanosized TiO₂. On the basis of analysis above, we carry out this work for studying the influence for the properties of photogenerated charge of TiO₂ modified by phosphoric acid and phosphate. The results are as follows:Phosphoric acid modification nanosized TiO₂ has been prepared by a sample impregnation method. The SPS response of TiO₂ modified by a suitable amount of phosphoric acid increased significantly. Through the combination of different external electric fields and atmosphere we suggest that the process of oxygen's capturing photogenerated electron is the key step to induce the response. The results showed that phosphoric acid modification with proper amount increased in the SPS responses and the lifetime of photoholes of TiO₂ nanocrystalline in oxygen gas. It demonstrated that phosphate modification was useful for photoelectrons to be captured by the adsorbed oxygen molecular, leading to the enhancement of the separation rate of photoinduced charges, which revealed the essential reason of the improvement of photocatalytic activity of TiO₂ nanocrystalline. High photovoltaic response means high efficiency photoinduced charge separation, thus explaining the improvement of photocatalytic activity.Cerium phosphate modification nanosized TiO₂ has been prepared by a sample impregnation method. The SPS response of TiO₂ modified by a suitable amount of cerium phosphoric decreased significantly. Through the combination of different external electric fields and atmosphere we suggest that the process of cerium ions's capturing photogenerated hole is due to the decrease of response. It also indicates that cerium ions can change the dynamics process of photogenerated charge, which may be beneficial to improve the photocatalytic performance. The above results show photogenerated electrons and holes can be captured by the absorbed O₂ and cerium ions respectively, which induces to the weak SPS reponse.This study has provided some reference methods and ideas for designing and synthesizing high performance TiO₂ based photocatalysts and provided some important experimental basis for enrich the theory of TiO₂ photocatalytic technology.