Construction,Mechanism And Properties Of Hydrotalcite Modified Structured G-C₃N₄ Photocatalyst

Since the 19th century,the environmental pollution caused by the rapid development of industrialization has brought great trouble and harm to human beings.Among them,the pollution of water bodies by phenols and antibiotics has attracted people’s high attention.Compared with the traditional wastewater treatment technology,photocatalytic oxidation technology has the characteristics of mild treatment conditions and low cost.As a new photocatalyst,g-C₃N₄ has been widely used in the field of photocatalytic degradation of pollutants because of its excellent thermochemical stability,good optical and photoelectrochemical properties.However,due to the problems of high photogenerated carrier recombination rate and low conductivity,the practical application of g-C₃N₄ is still limited.To solve this problem,firstly,g-C₃N₄ was modified to synthesize g-C₃N₄doped with non-metallic elements with special morphology,and then the modified g-C₃N₄ was compounded with hydrotalcite to construct a heterostructure with strong interface interaction.The photocatalytic degradation effects of phenol,2,4,6-trichlorophenol,p-nitrophenol and ciprofloxacin,and the mesoscale mechanism were studied.The main research contents of this paper are as follows:（1）NiFe-LDHs and P-TCN heterostructure photocatalysts with strong interface interaction were constructed,The interface structure was changed by adjusting the number of surface defects of g-C₃N₄.Combined with Doppler broadening Positron Annihilation Technology and EPR characterization technology,the interface electron transfer effect under light was quantitatively revealed.It was found that there was a synergistic effect between the surface defects and the interface of P-TCN,which was helpful to better understand the working mechanism of heterojunction interface.Firstly,P-doped tubular g-C₃N₄（P-TCN）was prepared using phosphoric acid as phosphorus source.Then,a series of NiFe-LDHs/P-TCN photocatalysts were prepared by in-situ modification of NiFe-LDHs on the surface of P-TCN in a vertical orientation with NH₄F as structure guiding agent.Phenol,2,4,6-trichlorophenol and p-nitrophenol were used as model pollutants.When the content of NiFe-LDHs was 35%,it showed the best photocatalytic performance.The degradation ratio of three pollutants（10mg/L）can reach more than 90%within 90 min under the using amount of catalyst of 1 g/L.（2）C-CN-550 was prepared by a secondary roasting method,using tetraphenylphosphorus chloride as carbon precursor and introducing aromatic ring into g-C₃N₄ structure,compounded with ZnCr-LDHs with good visible light response to prepare a series of ZnCr-LDHs/C-CN-550photocatalysts.For degradation of CIP in visible light（λ>420 nm）,19%ZnCr-LDHs/C-CN-550 has the best performance.Nearly 100%performance was achieved at 30 minutes,and its degradation rate is 8.25 times that of bulk C₃N₄.The enhancement of performance improvement mainly comes from three aspects.The first is the introduction of aromatic ring structure,which enhances the delocalization effect of electrons in g-C₃N₄ and promotes the absorption of visible light.Second,the formation of porous structure increases the specific surface area of the catalyst,enhances the electron transport effect,and adjusts the energy band structure to make the potential of the conduction band more negative,then enhance the activity.Thirdly,loading of ZnCr-LDHs and C-CN-550 forms a Z-scheme heterostructure.the response ability of the catalyst in visible light region was further expanded and the migration and separation ability of photogenerated carriers was significantly improved,which promoted the reaction.