毕业设计（论文）Preparation and application of g-C3N4TiO2 composite with visible light photocatalytic activity.docxVIP

Abstract The collection of solar energy through photocatalysts and subsequent production of renewable energy sources (such as hydrogen) is an attractive and sustainable solution to our energy problem. Due to the potential in environmental and energy-related applications, metal oxide semiconductor photocatalysts have attracted worldwide attention.Most of the photocatalysts studied previously had the problem of low quantum efficiency, which was mainly due to the rapid recombination of charge within the photocatalyst,while the charge was slowly transferred at the interface of the photocatalyst. For example, electron-hole recombination in TiO2 usually occurs in the nanosecond time scale, whereas the interface charge transfer usually takes almost a microsecond time. This may be worse when applying internal modifications such as doping to improve their optical performance. However, when the heterojunction is formed among the different semiconductors, the charge recombination can be remarkably suppressed. g-C3N4 has been widely recognized as an ideal semiconductor for the manufacture of heterostructures with various semiconductors for the following reasons: (1) visible light absorption bandgap (~ 2.75eV)，and its efficient photocatalytic performance under visible light (2) minimum conduction band (CB) (-1.12eV vs. NHE) promoting the electron to another semiconductor’s CB and thus its photogenerated electrons have a strong reducing ability. (3) cheap and simple synthesis which can have a wide use in production practice.TiO2 (P25) is one of the polymorphs of titania having n-type electron conductivity. Relatively open structure , a large number of surface OH groups and simple synthesis method makes a variety of modifications and large-scale production becomes feasible.For the first time, g-C3N4/TiO2 is synthesized by hydrothermal method using melamine sponge and TiO2 (P25) as the raw materials.At the same time, g-C3N4/TiO2 is also prepared by the same hydrothermal method usin