Synthesis Of Metal Sulfides And G-C₃N₄ Composites And Their Photocatalytic Degradation Of Volatile Organic Compounds

The rapid development of industry has led to the emission of large quantities of volatile organic pollutants?VOCs?,which has caused great harm to the ecological environment and human health.The control and removal technology of VOCs has become one of the research hotspots in the current environmental field.Photocatalytic technology has shown great potential for degrading VOCs due to the utilization of solar energy,strong mineralization ability,and no secondary pollution.However,the classic photocatalysts usually suffer from some problems such as narrow light absorption range,easy recombination of photogenerated carriers,and low quantum efficiency,which seriously restricts the application of photocatalytic technology in the degradation of VOCs.It is of great significance to develop new photocatalysts for the efficient removal of VOCs.In this thesis,the tailoring of the morphology and the composite with g-C₃N₄ have been employed to improve the photocatalytic activity of metal sulfides,such as MoS₂ and AgInS₂ specially.The main results are shown as follows:?1?MoS₂@g-C₃N₄ core-shell nanospheres were prepared by hydrothermal method and ultrasonic electrostatic adhesion method.The X-ray photoelectron spectroscopy?XPS?demonstrated that strong electron interactions occurred after the coupling.The UV-visible diffuse reflectance?DRS?and fluorescence?PL?data analysis showed that the MoS₂@g-C₃N₄ core-shell nanospheres expanded the light absorption region and reduced the rate of photoelectron-hole recombination.By employing in-situ FTIR spectroscopy and using toluene as a model of VOCs,the efficiency of photocatalytic degradation of MoS₂@g-C₃N₄ core-shell nanospheres under the irradiation of visible light for 8 hours was 81%,which was 1.32 and 9.59 times than those of MoS₂ nanospheres and g-C₃N₄,respectively.The hydroxyl radical and superoxide radical are the main reactive oxygen species during the photocatalytic reaction.It can be found that a series of intermediate products,such as benzyl alcohol,benzaldehyde,and benzoic acid,were generated during the photocatalytic degradation of toluene from the in situ FTIR spectra and the final products after the mineralization were CO2 and H2 O.?2?AgInS₂/g-C₃N₄ composites were synthesized in situ by hydrothermal method using g-C₃N₄ nanosheets as template.From the scanning electron microscope?SEM?analysis,it was found that AgInS₂ was successfully loaded on the g-C₃N₄ nanosheets to form a composite material.The DRS,PL and surface photovoltage spectra?SPV?analysis showed that the AgInS₂/g-C₃N₄ composite broadened the light absorption region,improved the photoelectron-hole separation rate and decreased the recombination.The photocatalytic performance of AgInS₂/g-C₃N₄ composites was investigated by using ortho-dichlorobenzene??-DCB?as the target contaminant.The efficiency of photocatalytic degradation of gas phase o-DCB by AgInS₂/g-C₃N₄ under the irradiation of visible light for 6 h reached 61.2%,which was 2.1 and 1.67 times than those of g-C₃N₄ nanosheets and AgInS₂.From the in situ FTIR spectra,it can be found that the final product of photocatalytic degradation of gas phase ?-DCB is carbon dioxide,water and so on.