Quantum Dots Modified Titanium Dioxide And Its Photocatalytic Properties

Because the photocatalytic reaction has the advantages of energy saving,low pollution and thorough degradation ability,the use of photocatalytic technology to deal with environmental pollution and water pollution has become a promising research.Among the many photocatalytic materials,TiO₂is considered to be one of the most promising photocatalytic materials due to its advantages of high activity,high stability,non-toxicity,non-pollution and suitable energy band position.However,it still has some shortcomings.The two major problems of low light utilization and low quantum efficiency have restricted its industrial application to a certain extent.In order to increase the application range of photocatalysis technology,it is of great significance to develop a new type of high-activity TiO₂catalyst.Therefore,in this paper,aiming at the two major problems of low light utilization efficiency and low quantum efficiency of TiO₂,a series of modification studies have been carried out to improve its photocatalytic activity.The specific research is as follows:（1）Preparation of GQDs/TiO₂photocatalyst.Firstly,glucose was used as raw material to prepare yellow-brown GQDs by hydrothermal method,and then GQDs/TiO₂photocatalyst was prepared by low-temperature gel-sol method.Characterize and analyze the phase,morphology,and photoelectric properties of the catalyst.The results show that before and after the addition of GQDs,TiO₂is a mixture of amorphous and anatase,but after adding GQDs,the proportion of anatase decreases,which increases the probability of electrons and holes meeting.The ultraviolet-visible spectrogram shows that the addition of GQDs has no effect on the light absorption intensity and range of TiO₂.Fluorescence analysis spectra and instantaneous photocurrent proved that adding a certain amount of GQDs effectively improved the separation and transport of charges,which is also the reason for the increased activity of the GQDs/TiO₂catalyst.Through the degradation experiment of the methyl orange solution,it can be seen that when the added amount of GQDs is 1%of the mass of TiO₂,the degradation rate of2.5h reaches 79.8%,and the first-order kinetic constant is 0.01038 min^-1,which is 1.35times that of pure TiO₂.（2）Preparation of g-C₃N₄QDs/GQDs/TiO₂photocatalyst.First,melamine was used as raw material to prepare g-C₃N₄QDs,and then g-C₃N₄QDs/GQDs/TiO₂photocatalyst was prepared by simple physical methods.It can be seen from the transmission electron microscope spectrum that g-C₃N₄QDs was successfully loaded on the surface of the GQDs/TiO₂photocatalyst.The ultraviolet-visible spectrogram shows that with the increase of g-C₃N₄QDs content,the light absorption intensity and light absorption range of the catalyst increase.Fluorescence analysis spectrum and instantaneous photocurrent proved that adding a certain amount of g-C₃N₄QDs effectively improved the separation and transfer of charges.Through the degradation experiment of methyl orange solution,when the amount of g-C₃N₄QDs added is 2%of the mass of TiO₂,the degradation rate of 2.5h reaches 90.5%,and the first-order kinetic constant is 0.01544 min^-1,which is GQDs/TiO₂1.46 times.（3）Preparation of Cd SQDs/GQDs/TiO₂photocatalyst.First,sodium sulfide and cadmium chloride are used as raw materials to prepare Cd SQDs,and then Cd SQDs/GQDs/TiO₂photocatalysts are prepared by simple physical methods.It can be seen from the transmission electron microscope spectrum that Cd SQDs were successfully loaded on the surface of the GQDs/TiO₂photocatalyst.The ultraviolet-visible spectrogram shows that with the increase of Cd SQDs content,the light absorption intensity and light absorption range of the catalyst both increase.Fluorescence analysis spectrum and instantaneous photocurrent proved that adding a certain amount of Cd SQDs effectively improved the separation and transfer of charges.Through the degradation experiment of methyl orange solution,when the amount of Cd SQDs added is 3%of the mass of TiO₂,the degradation rate of 2.5h reaches 92.3%,and the first-order kinetic constant is 0.01668 min^-1,which is GQDs/TiO₂1.61 times.