Preparation And Application Of Photocatalytic Composite Materials Based On G-C₃N₄

With the rapid development of science and technology,the degree of industrialization is getting higher and higher,water pollution has increasingly become a problem to be solved by human beings.In the water pollution,the particularly serious problems are organic pollutants and heavy metal pollutants.Therefore,how to deal with waste water has become an urgent problem that humans need to solve.Semiconductor photocatalytic technology is a water treatment method that is very convenient and does not generate secondary contaminants.Graphene-like carbon nitride is a non-toxic,non-harmful,inexpensive,simple composition and is considered a promising non-metal semiconductor photocatalyst.But due to its low absorption of light,the photogenerated electron-hole pairs are also easily recombined,therefore,the optoelectronic properties can be improved by selecting a suitable semiconductor to form a heterojunction with the semiconductor.While the SnS₂ as an n-type semiconductor material has a bandgap of about 2.4eV,an appropriate bandgap can produces better photoelectric properties,so that its application in the field of optoelectronics is very extensive.Based on this,we compared the SnS₂ synthesized at different temperatures and selected the SnS₂ with higher conductivity band than g-C₃N₄ at a certain temperature then combined it with g-C₃N₄ in situ.A series of SnS₂/g-C₃N₄ nanocomposites with mass ratio are prepared by in-situ hydrothermal method.In wastewater,there will be many kinds of pollutants in most cases,such as organic pollutants and heavy metal pollutants.In this paper,the performance of SnS₂/g-C₃N₄ composites which oxidize RhB and reduce Cr（Ⅵ）at the same time under visible light were studied by using common organic pollutants RhB and inorganic pollutants Cr（Ⅵ）as the mixed substrates.Compared photocatalytic performance of composite materials under different ratios,The experimental results show that the oxidative degradation of RhB is 80%by the best composite SCN30after light irradiation for 120 minutes,while the reduction of Cr（VI）is 99.8%.Through the capture experiments,it was concluded that the decomposition of RhB is mainly O₂^-and the reduction of Cr（VI）is e^-reduction.its possible mechanism can be concluded that SnS₂ electrons will transfer to the g-C₃N₄ conduction band to undergo reduction reaction and the holes on g-C₃N₄ will transfer to the SnS₂ valence band to undergo oxidation reaction in the composites material.Composite material are charaterizated by XRD,UV-Vis DRS,FT-IR,and low temperature N₂adsorption/desorption tests The SCN30 material with the best performance was analyzed by TEM and SEM,to analyze the morphology,structure.the results show that SnS₂ is wrapped on the surface of g-C₃N₄ and forms heterojunction which can increase the absorption rate of light and reduce the recombination rate of photogenerated electron-hole pair.Analyzed the photocatalysts under different pH conditions,the experimental results show that different pH values can affect the photocatalytic degradation capability.At pH=12,the degradation ability of SCN30was lower than that of pH=3,but the degradation ability of pH=6 was the highest.