Photocatalytic Properties Research Of Layered Thiocyanate And Its Complexes

Global warming caused by excessive CO2 emissions poses challenges to human survival;On the other hand,water pollution caused by industrial wastewater discharge seriously threatens human survival.Among many treatment methods,photocatalytic technology has low energy consumption and high efficiency,which is widely used in CO2 treatment and wastewater degradation.However,the traditional photocatalyst only has light response in the ultraviolet band,resulting in low utilization rate of sunlight and low catalytic efficiency.Accordingly,two-dimensional layered(C3N3S3)n and(C3N3S3)n/rGO composites were synthesized using C3H3N3S3 as the precursor in this paper,and a new visible light response photocatalytic system was successfully constructed.The main research contents and results of this paper are as follows:(1)Catalytic purification of water by layered(C3N3S3)n under visible light.Two-dimensional layered(C3N3S3)n was prepared by wet chemical synthesis at room temperature,and a novel semiconductor photocatalyst bridged by disulfide was constructed.It was applied to the photocatalytic degradation of rhodamine B(RhB)under visible light irradiation.When the solution pH was 5,the temperature was 50℃,the dosage of(C3N3S3),was 10 mg,and the visible light irradiation time was 100 min,the degradation rate of RhB reached 92%.This is because under the excitation of visible light,the photogenerated electrons(e-)in semiconductor(C3N3S3)n transfers from valence band(VB)to conduction band(CB),and e-oxidizes O2 to form superoxide radical(·O2-),·O2-strongly oxidizes and degrades RhB,while leaving holes(h+)in VB to oxidize pollutants directly.(2)Layered(C3N3S3)n can catalyze the reduction of CO2 under visible light.Two-dimensional lay ered(C3N3S3)n was applied to the photocatalytic reduction of CO2 under visible light irradiation.After 8 h of visible light irradiation,the yields of HCOOH and HCHO were 30 μg/g and 16 μg/g,respectively,and the yields of CO and CH4 were 40 μL/L and 9.5μL/L,respectively.To furth er improve the reduction efficiency of the system,three kinds of sacrificial agents(triethanolamine,ethylene glycol and ascorbic acid)were added in the system,and triethanolamine was better than ethylene glycol and ascorbic acid.When triethanolamine was added into the system,the yields of HCOOH,CO,HCHO,and CH4 increased to 100 μg/g,80 μL/L,55μg/g and 20 μL/L,respectively.The yields increased by two times,and the CO2 reduction efficiency was improved.This is due to the depletion of valence band holes by triethanolamine,which promotes the electron-hole separation in(C3N3S3)n and makes(C3N3S3)n have higher CO2 reduction activity.(3)Layered(C3N3S3)n/rGO visible light catalytic reduction of CO2.Although(C3N3S3)n exhibits CO2 reduction activity under visible light,in order to further improve its reduction efficiency,layered(C3N3S3)n/rGO composites were fabricated by wet chemical synthesis using two-dimensional graphite oxide(GO)as carrier.(C3N3S3)n/rGO has better CO2 reduction activity than(C3N3S3)n.The yields of HCOOH,CO,HCHO and CH4 are 80 μg/g,85 μL/L,40μg/g and 20 μL/L,respectively,which are 2.6 times higher than that of(C3N3S3)n alone.This is due to the fact that under visible light excitation,semiconductor(C3N3S3)n transfers electrons in its conduction band to rGO,which effectively improves the separation of electron-hole pairs and inhibits the recombination of photogenerated carriers.When triethanolamine electron sacrificial agent was introduced into the reaction system,the yields of HCOOH,CO,HCHO and CH4 increased to 200 μg/g,220 μL/L,80 μg/g and 50μL/L,and the yields increased by 2.4 times,triethanolamine enhanced the photocatalytic activity of(C3N3S3)n/rGO for CO2 reduction.