Preparation And Properties Of Graphite Phase Carbon Nitride With Tin-based Compound Composite

Water pollution is one of the most urgent problems to be solved at present.Semiconductor photocatalysis technology is considered to be a simple and efficient method to treat pollutants in wastewater.Graphite phase carbon nitride（g-C₃N₄）is a kind of nonmetallic semiconductor with abundant raw materials,simple synthesis,non-toxic and harmless.However,its development and application are limited due to its high photo-generated electron hole recombination rate and limited light absorption range.The photocatalytic performance of g-C₃N₄can be improved effectively by selecting a semiconductor with a band gap matching to form a heterojunction with g-C₃N₄.In this paper,g-C₃N₄was prepared from urea,and a series of photocatalysts were prepared by compounding g-C₃N₄with tin compounds.The main research contents are as follows:1.Preparation and properties of SnO/g-C₃N₄Using urea as the precursor,g-C₃N₄was prepared by thermal condensation at 550℃,and SnO was prepared by stannous chloride dihydrate,sodium hydroxide and trisodium citrate.SnO/g-C₃N₄photocatalyst with different SnO content was synthesized by ultrasonic-assisted method,and characterized by SEM,XRD and UV-Vis.Rhodamine B（RhB）was used as a simulated pollutant source in photocatalytic degradation experiments.The results showed that the photocatalytic performance of SnO/g-C₃N₄was significantly higher than that of pure g-C₃N₄under certain SnO loading,and the photocatalytic performance of SnO/g-C₃N₄prepared with 15 wt%SnO was the best.The degradation efficiency of RhB reached 93.28%after 120 min of UV irradiation.g-C₃N₄only degraded 42.6%after 120 min.The composite has good UV light absorption performance,and the transmission and separation ability of photogenerated electron hole pairs of the composite is significantly improved,which is attributed to the formation of Z-type heterojunction by SnO/g-C₃N₄.2.Preparation and properties of SnS₂/g-C₃N₄Taking urea as the precursor,g-C₃N₄was prepared by thermal condensation at 550℃,and SnS₂was prepared by tin tetrachloride pentahydrate and thiourea.SnS₂/g-C₃N₄photocatalyst with different SnS₂content was synthesized by solvothermal method.In the photocatalytic degradation experiment,rhodamine B was used as the pollutant simulation source.The results show that the photocatalytic performance of SnS₂/g-C₃N₄is obviously better than that of pure g-C₃N₄.The photocatalytic performance of SnS₂/g-C₃N₄is the best when the composite amount of SnS₂is 85 wt%.The degradation efficiency of RhB reaches59.01%after 120 minutes of irradiation under 50 W LED lamp.The degradation rates of g-C₃N₄and SnS₂were 34.66%and 38.32%.When SnS₂and g-C₃N₄are recombined,the photogenerated electrons in the g-C₃N₄conduction band are transferred to the SnS₂conduction band,and the photogenerated holes in the valence band of SnS₂are transferred to the valence band of g-C₃N₄,which promotes the separation rate of photogenerated carriers and effectively improves the photocatalytic performance.3.Preparation and properties of Ag/SnS₂/g-C₃N₄SnS₂/g-C₃N₄photocatalyst was synthesized by solvothermal method.Silver nitrate was used as the silver source,and the ternary Ag/SnS₂/g-C₃N₄photocatalyst with different Ag content was reduced by ultraviolet light and ultrasonic assisted method.Rhodamine B was used as the simulated pollutant in the photocatalytic degradation experiment.The results show that the photocatalytic performance of ternary Ag/SnS₂/g-C₃N₄composites is significantly higher than that of g-C₃N₄and SnS₂/g-C₃N₄at a certain Ag loading capacity,and the best photocatalytic performance of Ag/SnS₂/g-C₃N₄is obtained when the Ag loading capacity is0.0022 wt%.The degradation efficiency of RhB reached 87.79%,and the degradation rates of g-C₃N₄,SnS₂and SnS₂/g-C₃N₄were 34.66%,38.32%and 59.01%after 120 min irradiation under 50 W LED lamp.This is because Ag/SnS₂/g-C₃N₄forms a Z-type heterojunction.Ag,as an intermediate,is used to bridge the two kinds of semiconductors.The Ag sandwged between the two semiconductors acts as the electronic medium,which effectively promotes photoexcited charge transfer and improves the separation rate of photogenerated carriers.The photocatalytic performance was better than that of SnS₂,g-C₃N₄and SnS₂/g-C₃N₄.