| Semiconductor photocatalysis technology has a good application prospect for the treatment of organic pollution.It is of great significance to research and develop photocatalytic materials with visible light response,high efficiency and low cost.In this paper,on the basis of optimizing the composite method and ratio of NH2-MIL-125(Ti)/C3N4 binary composites,dual Z-scheme Ag6Si2O7/NH2-MIL-125(Ti)/C3N4 ternary composite photocatalytic materials were successfully prepared by ultrasound-assisted in-situ deposition method.The samples were characterized by XRD,HRTEM,FESEM,EDS,FT-IR,UV-Vis DRS,XPS,etc.The results show that,in the ternary composites prepared under the optimized conditions,NH2-MIL-125(Ti)with coin-like structure was distributed on the lamellar C3N4 surface.Ag6Si2O7nanoparticles were randomly anchored on the surface of NH2-MIL-125(Ti)/C3N4,and there was a strong interaction between Ag6Si2O7,NH2-MIL-125(Ti)and C3N4.The three semiconductors were closely combined with each other,the absorption edge had an obvious redshift compared with C3N4as main component in the ternary composite,and the absorption of visible light was obviously enhanced.The effects of the mass ratios of NH2-MIL-125(Ti)/C3N4 to Ag6Si2O7 on the photocatalytic performance of the Ag6Si2O7/NH2-MIL-125(Ti)/C3N4 ternary composite were investigated.The results show that the ternary composite material had the best photocatalytic activity when the mass ratio of NH2-MIL-125(Ti)/C3N4 to Ag6Si2O7 was 20:1,and the removal rate of Rh B reached 87.5%after 90 minutes under visible light irradiation,much higher than 27.5%of pristine Ag6Si2O7 and81.1%of NH2-MIL-125(Ti)/C3N4 binary composite.Its photocatalytic apparent rate constant was15.6 times that of pristine Ag6Si2O7 and 1.3 times that of NH2-MIL-125(Ti)/C3N4 binary composite.It also had good photocatalytic activity for colorless organic pollutants.The apparent rate constant of photocatalysis for tetracycline was 1.42 times that of NH2-MIL-125(Ti)/C3N4binary composite catalyst,and 1.69 times that of pristine Ag6Si2O7;The photocatalytic apparent rate constant for ethenzamide was 7.98 times that of the NH2-MIL-125(Ti)/C3N4 binary composite and 1.75 times that of pristine Ag6Si2O7.After repeated use for three times,the removal rate of Rh B was still 79.3%,and showed good stability.Mechanism studies using PL,EIS,ESR and active species capture experiments showed that compared with pristine Ag6Si2O7,NH2-MIL-125(Ti)and C3N4 and NH2-MIL-125(Ti)/C3N4 binary composites,the ternary composite had the lowest PL emission peak intensity and the smallest Nyquist semicircle radius,which effectively inhibited the recombination of e--h+pairs;h+and·O2-were the main active species in the photocatalytic process of the ternary composite.·OH radical also participated in the photocatalytic reaction;three semiconductors in the ternary composite formed a tight dual-Z heterostructure,which explained the formation of active species and the degradation of organic pollutants during the photocatalytic process. |
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